diff --git a/include/swift/IDE/CodeCompletion.h b/include/swift/IDE/CodeCompletion.h
index 150f6793097..66c4f57c83d 100644
--- a/include/swift/IDE/CodeCompletion.h
+++ b/include/swift/IDE/CodeCompletion.h
@@ -399,6 +399,7 @@ public:
 
 private:
   CodeCompletionString *const CompletionString;
+  StringRef ModuleName;
   StringRef BriefDocComment;
   ArrayRef<StringRef> AssociatedUSRs;
 
@@ -416,17 +417,14 @@ private:
   CodeCompletionResult(SemanticContextKind SemanticContext,
                        unsigned NumBytesToErase,
                        CodeCompletionString *CompletionString,
-                       const Decl *AssociatedDecl,
-                       bool NotRecommended,
-                       StringRef BriefDocComment,
+                       const Decl *AssociatedDecl, StringRef ModuleName,
+                       bool NotRecommended, StringRef BriefDocComment,
                        ArrayRef<StringRef> AssociatedUSRs)
       : Kind(ResultKind::Declaration),
         SemanticContext(unsigned(SemanticContext)),
-        NotRecommended(NotRecommended),
-        NumBytesToErase(NumBytesToErase),
-        CompletionString(CompletionString),
-        BriefDocComment(BriefDocComment),
-        AssociatedUSRs(AssociatedUSRs) {
+        NotRecommended(NotRecommended), NumBytesToErase(NumBytesToErase),
+        CompletionString(CompletionString), ModuleName(ModuleName),
+        BriefDocComment(BriefDocComment), AssociatedUSRs(AssociatedUSRs) {
     assert(AssociatedDecl && "should have a decl");
     AssociatedDeclKind = unsigned(getCodeCompletionDeclKind(AssociatedDecl));
     assert(CompletionString);
@@ -456,6 +454,8 @@ public:
     return CompletionString;
   }
 
+  StringRef getModuleName() const { return ModuleName; }
+
   StringRef getBriefDocComment() const {
     return BriefDocComment;
   }
@@ -483,6 +483,10 @@ struct CodeCompletionResultSink {
 
   std::vector<CodeCompletionResult *> Results;
 
+  /// A single-element cache for module names stored in Allocator, keyed by a
+  /// clang::Module * or swift::Module *.
+  std::pair<void *, StringRef> LastModule;
+
   CodeCompletionResultSink()
       : Allocator(std::make_shared<llvm::BumpPtrAllocator>()) {}
 };
diff --git a/lib/IDE/CodeCompletion.cpp b/lib/IDE/CodeCompletion.cpp
index 00370cb5e15..420bc2428e0 100644
--- a/lib/IDE/CodeCompletion.cpp
+++ b/lib/IDE/CodeCompletion.cpp
@@ -401,6 +401,19 @@ void CodeCompletionResultBuilder::addChunkWithText(
   addChunkWithTextNoCopy(Kind, copyString(*Sink.Allocator, Text));
 }
 
+void CodeCompletionResultBuilder::setAssociatedDecl(const Decl *D) {
+  assert(Kind == CodeCompletionResult::ResultKind::Declaration);
+  AssociatedDecl = D;
+
+  if (auto *ClangD = D->getClangDecl())
+    CurrentModule = ClangD->getOwningModule();
+  // FIXME: macros
+  // FIXME: imported header module
+
+  if (!CurrentModule)
+    CurrentModule = D->getModuleContext();
+}
+
 StringRef CodeCompletionContext::copyString(StringRef Str) {
   return ::copyString(*CurrentResults.Allocator, Str);
 }
@@ -472,10 +485,27 @@ CodeCompletionResult *CodeCompletionResultBuilder::takeResult() {
     } else {
       BriefComment = AssociatedDecl->getBriefComment();
     }
+
+    StringRef ModuleName;
+    if (CurrentModule) {
+      if (Sink.LastModule.first == CurrentModule.getOpaqueValue()) {
+        ModuleName = Sink.LastModule.second;
+      } else {
+        if (auto *C = CurrentModule.dyn_cast<const clang::Module *>()) {
+          ModuleName = copyString(*Sink.Allocator, C->getFullModuleName());
+        } else {
+          ModuleName = copyString(
+              *Sink.Allocator,
+              CurrentModule.get<const swift::Module *>()->getName().str());
+        }
+        Sink.LastModule.first = CurrentModule.getOpaqueValue();
+        Sink.LastModule.second = ModuleName;
+      }
+    }
+
     return new (*Sink.Allocator) CodeCompletionResult(
-        SemanticContext, NumBytesToErase, CCS, AssociatedDecl,
-        /*NotRecommended=*/false,
-        copyString(*Sink.Allocator, BriefComment),
+        SemanticContext, NumBytesToErase, CCS, AssociatedDecl, ModuleName,
+        /*NotRecommended=*/false, copyString(*Sink.Allocator, BriefComment),
         copyAssociatedUSRs(*Sink.Allocator, AssociatedDecl));
   }
 
diff --git a/lib/IDE/CodeCompletionResultBuilder.h b/lib/IDE/CodeCompletionResultBuilder.h
index 77bd2474552..a6f0d76580c 100644
--- a/lib/IDE/CodeCompletionResultBuilder.h
+++ b/lib/IDE/CodeCompletionResultBuilder.h
@@ -18,8 +18,13 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 
+namespace clang {
+class Module;
+}
+
 namespace swift {
 class Decl;
+class Module;
 
 namespace ide {
 
@@ -31,6 +36,8 @@ class CodeCompletionResultBuilder {
   const Decl *AssociatedDecl = nullptr;
   unsigned CurrentNestingLevel = 0;
   SmallVector<CodeCompletionString::Chunk, 4> Chunks;
+  llvm::PointerUnion<const swift::Module *, const clang::Module *>
+      CurrentModule;
 
   void addChunkWithText(CodeCompletionString::Chunk::ChunkKind Kind,
                         StringRef Text);
@@ -69,10 +76,7 @@ public:
     NumBytesToErase = N;
   }
 
-  void setAssociatedDecl(const Decl *D) {
-    assert(Kind == CodeCompletionResult::ResultKind::Declaration);
-    AssociatedDecl = D;
-  }
+  void setAssociatedDecl(const Decl *D);
 
   void addAccessControlKeyword(Accessibility Access) {
     switch (Access) {