diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index cd4eeed7522..8fa124868cc 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11127,7 +11127,7 @@ namespace ts {
          * property is computed by inferring from the source property type to X for the type
          * variable T[P] (i.e. we treat the type T[P] as the type variable we're inferring for).
          */
-        function inferTypeForHomomorphicMappedType(source: Type, target: MappedType): Type {
+        function inferTypeForHomomorphicMappedType(source: Type, target: MappedType, mappedTypeStack: [Type, Symbol][]): Type {
             const properties = getPropertiesOfType(source);
             let indexInfo = getIndexInfoOfType(source, IndexKind.String);
             if (properties.length === 0 && !indexInfo) {
@@ -11160,7 +11160,7 @@ namespace ts {
 
             function inferTargetType(sourceType: Type): Type {
                 inference.candidates = undefined;
-                inferTypes(inferences, sourceType, templateType);
+                inferTypes(inferences, sourceType, templateType, 0, mappedTypeStack);
                 return inference.candidates ? getUnionType(inference.candidates, /*subtypeReduction*/ true) : emptyObjectType;
             }
         }
@@ -11178,7 +11178,7 @@ namespace ts {
             return undefined;
         }
 
-        function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0) {
+        function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0, mappedTypeStack?: [Type, Symbol][]) {
             let symbolStack: Symbol[];
             let visited: Map<boolean>;
             inferFromTypes(originalSource, originalTarget);
@@ -11395,7 +11395,12 @@ namespace ts {
                         // such that direct inferences to T get priority over inferences to Partial<T>, for example.
                         const inference = getInferenceInfoForType((<IndexType>constraintType).type);
                         if (inference && !inference.isFixed) {
-                            const inferredType = inferTypeForHomomorphicMappedType(source, <MappedType>target);
+                            if (contains(mappedTypeStack, [source, target.symbol], ([s1,t1],[s2,t2]) => s1 === s2 && t1 === t2)) {
+                                return;
+                            }
+                            (mappedTypeStack || (mappedTypeStack = [])).push([source, target.symbol]);
+                            const inferredType = inferTypeForHomomorphicMappedType(source, <MappedType>target, mappedTypeStack);
+                            mappedTypeStack.pop();
                             if (inferredType) {
                                 const savePriority = priority;
                                 priority |= InferencePriority.MappedType;