diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index f4ddf1d8319..b6700d21a70 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -681,10 +681,22 @@ namespace ts {
             return getSpanOfTokenAtPosition(sourceFile, node.pos);
         }
 
-        const pos = nodeIsMissing(errorNode)
+        const isMissing = nodeIsMissing(errorNode);
+        const pos = isMissing
             ? errorNode.pos
             : skipTrivia(sourceFile.text, errorNode.pos);
 
+        // These asserts should all be satisfied for a properly constructed `errorNode`.
+        // Upstream from https://github.com/Microsoft/TypeScript/issues/20809.
+        if (isMissing) {
+            Debug.assert(pos === errorNode.pos);
+            Debug.assert(pos === errorNode.end);
+        }
+        else {
+            Debug.assert(pos >= errorNode.pos);
+            Debug.assert(pos <= errorNode.end);
+        }
+
         return createTextSpanFromBounds(pos, errorNode.end);
     }
 
diff --git a/src/services/refactors/extractSymbol.ts b/src/services/refactors/extractSymbol.ts
index e3a2763b783..9b397584fed 100644
--- a/src/services/refactors/extractSymbol.ts
+++ b/src/services/refactors/extractSymbol.ts
@@ -335,6 +335,15 @@ namespace ts.refactor.extractSymbol {
                 Continue = 1 << 1,
                 Return = 1 << 2
             }
+
+            // This assert is upstream from https://github.com/Microsoft/TypeScript/issues/20809.
+            // We believe it's true because the node is from the (unmodified) tree.
+            Debug.assert(nodeToCheck.pos <= nodeToCheck.end);
+
+            // This assert is upstream from https://github.com/Microsoft/TypeScript/issues/20809.
+            // For understanding how skipTrivia functioned:
+            Debug.assert(!positionIsSynthesized(nodeToCheck.pos));
+
             if (!isStatement(nodeToCheck) && !(isExpressionNode(nodeToCheck) && isExtractableExpression(nodeToCheck))) {
                 return [createDiagnosticForNode(nodeToCheck, Messages.statementOrExpressionExpected)];
             }