diff --git a/src/vs/workbench/browser/parts/editor/textResourceEditor.ts b/src/vs/workbench/browser/parts/editor/textResourceEditor.ts
index cf6a9146b7d5720c7cd8b433a21bac530c0c010b..0f3197c7fad74eaf1067eeb29d5db9b7cc6f4d7c 100644
--- a/src/vs/workbench/browser/parts/editor/textResourceEditor.ts
+++ b/src/vs/workbench/browser/parts/editor/textResourceEditor.ts
@@ -4,7 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as nls from 'vs/nls';
-import { assertIsDefined, isFunction } from 'vs/base/common/types';
+import { assertIsDefined, isFunction, withNullAsUndefined } from 'vs/base/common/types';
 import { ICodeEditor, getCodeEditor, IPasteEvent } from 'vs/editor/browser/editorBrowser';
 import { TextEditorOptions, EditorInput, EditorOptions } from 'vs/workbench/common/editor';
 import { ResourceEditorInput } from 'vs/workbench/common/editor/resourceEditorInput';
@@ -26,6 +26,7 @@ import { IModeService } from 'vs/editor/common/services/modeService';
 import { PLAINTEXT_MODE_ID } from 'vs/editor/common/modes/modesRegistry';
 import { EditorOption, IEditorOptions } from 'vs/editor/common/config/editorOptions';
 import { basenameOrAuthority } from 'vs/base/common/resources';
+import { ModelConstants } from 'vs/editor/common/model';
 
 /**
  * An editor implementation that is capable of showing the contents of resource inputs. Uses
@@ -213,8 +214,8 @@ export class TextResourceEditor extends AbstractTextResourceEditor {
 	}
 
 	private onDidEditorPaste(e: IPasteEvent, codeEditor: ICodeEditor): void {
-		if (!e.mode || e.mode === PLAINTEXT_MODE_ID) {
-			return; // require a specific mode
+		if (e.range.startLineNumber !== 1) {
+			return; // only when pasting into first line (= likely empty document)
 		}
 
 		if (codeEditor.getOption(EditorOption.readOnly)) {
@@ -231,7 +232,24 @@ export class TextResourceEditor extends AbstractTextResourceEditor {
 			return; // require current mode to be unspecific
 		}
 
-		// Finally apply mode to model
-		this.modelService.setMode(textModel, this.modeService.create(e.mode));
+		let candidateMode: string | undefined = undefined;
+
+		// A mode is provided via the paste event so text was copied using
+		// VSCode. As such we trust this mode and use it if specific
+		if (e.mode) {
+			candidateMode = e.mode;
+		}
+
+		// A mode was not provided, so the data comes from outside VSCode
+		// We can still try to guess a good mode from the first line if
+		// the paste changed the first line
+		else {
+			candidateMode = withNullAsUndefined(this.modeService.getModeIdByFilepathOrFirstLine(textModel.uri, textModel.getLineContent(1).substr(0, ModelConstants.FIRST_LINE_DETECTION_LENGTH_LIMIT)));
+		}
+
+		// Finally apply mode to model if specified
+		if (candidateMode !== PLAINTEXT_MODE_ID) {
+			this.modelService.setMode(textModel, this.modeService.create(candidateMode));
+		}
 	}
 }