diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 133065b4e8..78ff1efc86 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1966,7 +1966,21 @@ namespace ts {
                 const file = find(moduleSymbol.declarations, isSourceFile);
                 const hasSyntheticDefault = canHaveSyntheticDefault(file, moduleSymbol, dontResolveAlias);
                 if (!exportDefaultSymbol && !hasSyntheticDefault) {
-                    error(node.name, Diagnostics.Module_0_has_no_default_export, symbolToString(moduleSymbol));
+                    if (hasExportAssignmentSymbol(moduleSymbol)) {
+                        const compilerOptionName = moduleKind >= ModuleKind.ES2015 ? "allowSyntheticDefaultImports" : "esModuleInterop";
+                        const exportEqualsSymbol = moduleSymbol.exports!.get(InternalSymbolName.ExportEquals);
+                        const exportAssignment = exportEqualsSymbol!.valueDeclaration;
+                        const err = error(node.name, Diagnostics.Module_0_can_only_be_default_imported_using_the_1_flag, symbolToString(moduleSymbol), compilerOptionName);
+
+                        addRelatedInfo(err, createDiagnosticForNode(
+                            exportAssignment,
+                            Diagnostics.This_module_is_declared_with_using_export_and_can_only_be_used_with_a_default_import_when_using_the_0_flag,
+                            compilerOptionName
+                        ));
+                    }
+                    else {
+                        error(node.name, Diagnostics.Module_0_has_no_default_export, symbolToString(moduleSymbol));
+                    }
                 }
                 else if (hasSyntheticDefault) {
                     // per emit behavior, a synthetic default overrides a "real" .default member if `__esModule` is not present
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index cd08731be0..0df9c2e4de 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -851,6 +851,10 @@
         "category": "Error",
         "code": 1258
     },
+    "Module '{0}' can only be default-imported using the '{1}' flag": {
+        "category": "Error",
+        "code": 1259
+    },
     "'with' statements are not allowed in an async function block.": {
         "category": "Error",
         "code": 1300
@@ -2156,6 +2160,10 @@
         "category": "Error",
         "code": 2593
     },
+    "This module is declared with using 'export =', and can only be used with a default import when using the '{0}' flag.": {
+        "category": "Error",
+        "code": 2594
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600
diff --git a/tests/baselines/reference/allowSyntheticDefaultImports6.errors.txt b/tests/baselines/reference/allowSyntheticDefaultImports6.errors.txt
index 80b9cf8d07..916f50162a 100644
--- a/tests/baselines/reference/allowSyntheticDefaultImports6.errors.txt
+++ b/tests/baselines/reference/allowSyntheticDefaultImports6.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/a.ts(1,8): error TS1192: Module '"tests/cases/compiler/b"' has no default export.
+tests/cases/compiler/a.ts(1,8): error TS1259: Module '"tests/cases/compiler/b"' can only be default-imported using the 'esModuleInterop' flag
 
 
 ==== tests/cases/compiler/b.d.ts (0 errors) ====
@@ -10,6 +10,7 @@ tests/cases/compiler/a.ts(1,8): error TS1192: Module '"tests/cases/compiler/b"'
 ==== tests/cases/compiler/a.ts (1 errors) ====
     import Foo from "./b";
            ~~~
-!!! error TS1192: Module '"tests/cases/compiler/b"' has no default export.
+!!! error TS1259: Module '"tests/cases/compiler/b"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/b.d.ts:4:1: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     export var x = new Foo();
     
\ No newline at end of file
diff --git a/tests/baselines/reference/es6ExportEqualsInterop.errors.txt b/tests/baselines/reference/es6ExportEqualsInterop.errors.txt
index 5b8e83b3cc..d7b992f2c1 100644
--- a/tests/baselines/reference/es6ExportEqualsInterop.errors.txt
+++ b/tests/baselines/reference/es6ExportEqualsInterop.errors.txt
@@ -1,16 +1,16 @@
 tests/cases/compiler/main.ts(15,1): error TS2693: 'z1' only refers to a type, but is being used as a value here.
 tests/cases/compiler/main.ts(21,4): error TS2339: Property 'a' does not exist on type '() => any'.
 tests/cases/compiler/main.ts(23,4): error TS2339: Property 'a' does not exist on type 'typeof Foo'.
-tests/cases/compiler/main.ts(27,8): error TS1192: Module '"interface"' has no default export.
-tests/cases/compiler/main.ts(28,8): error TS1192: Module '"variable"' has no default export.
-tests/cases/compiler/main.ts(29,8): error TS1192: Module '"interface-variable"' has no default export.
-tests/cases/compiler/main.ts(30,8): error TS1192: Module '"module"' has no default export.
-tests/cases/compiler/main.ts(31,8): error TS1192: Module '"interface-module"' has no default export.
-tests/cases/compiler/main.ts(32,8): error TS1192: Module '"variable-module"' has no default export.
-tests/cases/compiler/main.ts(33,8): error TS1192: Module '"function"' has no default export.
-tests/cases/compiler/main.ts(34,8): error TS1192: Module '"function-module"' has no default export.
-tests/cases/compiler/main.ts(35,8): error TS1192: Module '"class"' has no default export.
-tests/cases/compiler/main.ts(36,8): error TS1192: Module '"class-module"' has no default export.
+tests/cases/compiler/main.ts(27,8): error TS1259: Module '"interface"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(28,8): error TS1259: Module '"variable"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(29,8): error TS1259: Module '"interface-variable"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(30,8): error TS1259: Module '"module"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(31,8): error TS1259: Module '"interface-module"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(32,8): error TS1259: Module '"variable-module"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(33,8): error TS1259: Module '"function"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(34,8): error TS1259: Module '"function-module"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(35,8): error TS1259: Module '"class"' can only be default-imported using the 'esModuleInterop' flag
+tests/cases/compiler/main.ts(36,8): error TS1259: Module '"class-module"' can only be default-imported using the 'esModuleInterop' flag
 tests/cases/compiler/main.ts(39,21): error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.
 tests/cases/compiler/main.ts(45,21): error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.
 tests/cases/compiler/main.ts(47,21): error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.
@@ -76,34 +76,44 @@ tests/cases/compiler/main.ts(106,15): error TS2498: Module '"class-module"' uses
     // default import
     import x1 from "interface";
            ~~
-!!! error TS1192: Module '"interface"' has no default export.
+!!! error TS1259: Module '"interface"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:6:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x2 from "variable";
            ~~
-!!! error TS1192: Module '"variable"' has no default export.
+!!! error TS1259: Module '"variable"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:14:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x3 from "interface-variable";
            ~~
-!!! error TS1192: Module '"interface-variable"' has no default export.
+!!! error TS1259: Module '"interface-variable"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:26:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x4 from "module";
            ~~
-!!! error TS1192: Module '"module"' has no default export.
+!!! error TS1259: Module '"module"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:34:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x5 from "interface-module";
            ~~
-!!! error TS1192: Module '"interface-module"' has no default export.
+!!! error TS1259: Module '"interface-module"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:46:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x6 from "variable-module";
            ~~
-!!! error TS1192: Module '"variable-module"' has no default export.
+!!! error TS1259: Module '"variable-module"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:60:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x7 from "function";
            ~~
-!!! error TS1192: Module '"function"' has no default export.
+!!! error TS1259: Module '"function"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:65:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x8 from "function-module";
            ~~
-!!! error TS1192: Module '"function-module"' has no default export.
+!!! error TS1259: Module '"function-module"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:74:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x9 from "class";
            ~~
-!!! error TS1192: Module '"class"' has no default export.
+!!! error TS1259: Module '"class"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:82:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     import x0 from "class-module";
            ~~
-!!! error TS1192: Module '"class-module"' has no default export.
+!!! error TS1259: Module '"class-module"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/modules.d.ts:94:5: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
     
     // namespace import
     import * as y1 from "interface";
diff --git a/tests/baselines/reference/es6ImportDefaultBindingInEs5.errors.txt b/tests/baselines/reference/es6ImportDefaultBindingInEs5.errors.txt
index 604b27fd9c..924792bf98 100644
--- a/tests/baselines/reference/es6ImportDefaultBindingInEs5.errors.txt
+++ b/tests/baselines/reference/es6ImportDefaultBindingInEs5.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/es6ImportDefaultBindingInEs5_1.ts(1,8): error TS1192: Module '"tests/cases/compiler/es6ImportDefaultBindingInEs5_0"' has no default export.
+tests/cases/compiler/es6ImportDefaultBindingInEs5_1.ts(1,8): error TS1259: Module '"tests/cases/compiler/es6ImportDefaultBindingInEs5_0"' can only be default-imported using the 'esModuleInterop' flag
 
 
 ==== tests/cases/compiler/es6ImportDefaultBindingInEs5_0.ts (0 errors) ====
@@ -8,4 +8,5 @@ tests/cases/compiler/es6ImportDefaultBindingInEs5_1.ts(1,8): error TS1192: Modul
 ==== tests/cases/compiler/es6ImportDefaultBindingInEs5_1.ts (1 errors) ====
     import defaultBinding from "./es6ImportDefaultBindingInEs5_0";
            ~~~~~~~~~~~~~~
-!!! error TS1192: Module '"tests/cases/compiler/es6ImportDefaultBindingInEs5_0"' has no default export.
\ No newline at end of file
+!!! error TS1259: Module '"tests/cases/compiler/es6ImportDefaultBindingInEs5_0"' can only be default-imported using the 'esModuleInterop' flag
+!!! related TS2594 tests/cases/compiler/es6ImportDefaultBindingInEs5_0.ts:2:1: This module is declared with using 'export =', and can only be used with a default import when using the 'esModuleInterop' flag.
\ No newline at end of file
diff --git a/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.errors.txt b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.errors.txt
new file mode 100644
index 0000000000..d59ec8b42c
--- /dev/null
+++ b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.errors.txt
@@ -0,0 +1,15 @@
+/bar.ts(1,1): error TS1203: Export assignment cannot be used when targeting ECMAScript modules. Consider using 'export default' or another module format instead.
+/foo.ts(1,8): error TS1259: Module '"/bar"' can only be default-imported using the 'allowSyntheticDefaultImports' flag
+
+
+==== /bar.ts (1 errors) ====
+    export = bar;
+    ~~~~~~~~~~~~~
+!!! error TS1203: Export assignment cannot be used when targeting ECMAScript modules. Consider using 'export default' or another module format instead.
+    function bar() {}
+    
+==== /foo.ts (1 errors) ====
+    import bar from './bar';
+           ~~~
+!!! error TS1259: Module '"/bar"' can only be default-imported using the 'allowSyntheticDefaultImports' flag
+!!! related TS2594 /bar.ts:1:1: This module is declared with using 'export =', and can only be used with a default import when using the 'allowSyntheticDefaultImports' flag.
\ No newline at end of file
diff --git a/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.js b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.js
new file mode 100644
index 0000000000..5d433cba79
--- /dev/null
+++ b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.js
@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/exportAssignmentWithoutAllowSyntheticDefaultImportsError.ts] ////
+
+//// [bar.ts]
+export = bar;
+function bar() {}
+
+//// [foo.ts]
+import bar from './bar';
+
+//// [bar.js]
+function bar() { }
+//// [foo.js]
diff --git a/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.symbols b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.symbols
new file mode 100644
index 0000000000..8dca8faecf
--- /dev/null
+++ b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.symbols
@@ -0,0 +1,11 @@
+=== /bar.ts ===
+export = bar;
+>bar : Symbol(bar, Decl(bar.ts, 0, 13))
+
+function bar() {}
+>bar : Symbol(bar, Decl(bar.ts, 0, 13))
+
+=== /foo.ts ===
+import bar from './bar';
+>bar : Symbol(bar, Decl(foo.ts, 0, 6))
+
diff --git a/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.types b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.types
new file mode 100644
index 0000000000..d5c22d809c
--- /dev/null
+++ b/tests/baselines/reference/exportAssignmentWithoutAllowSyntheticDefaultImportsError.types
@@ -0,0 +1,11 @@
+=== /bar.ts ===
+export = bar;
+>bar : () => void
+
+function bar() {}
+>bar : () => void
+
+=== /foo.ts ===
+import bar from './bar';
+>bar : any
+
diff --git a/tests/cases/compiler/exportAssignmentWithoutAllowSyntheticDefaultImportsError.ts b/tests/cases/compiler/exportAssignmentWithoutAllowSyntheticDefaultImportsError.ts
new file mode 100644
index 0000000000..8513a6bdb6
--- /dev/null
+++ b/tests/cases/compiler/exportAssignmentWithoutAllowSyntheticDefaultImportsError.ts
@@ -0,0 +1,8 @@
+// @module: es2015
+
+// @Filename: /bar.ts
+export = bar;
+function bar() {}
+
+// @Filename: /foo.ts
+import bar from './bar';
\ No newline at end of file