diff --git a/src/vm/wren_compiler.c b/src/vm/wren_compiler.c
index 2ccf4bca..341d8e48 100644
--- a/src/vm/wren_compiler.c
+++ b/src/vm/wren_compiler.c
@@ -2208,12 +2208,18 @@ static void literal(Compiler* compiler, bool allowAssignment)
   emitConstant(compiler, compiler->parser->previous.value);
 }
 
+// A string literal that contains interpolated expressions.
+//
+// Interpolation is syntactic sugar for calling ".join()" on a list. So the
+// string:
+//
+//     "a %(b + c) d"
+//
+// is compiled roughly like:
+//
+//     ["a ", b + c, " d"].join()
 static void stringInterpolation(Compiler* compiler, bool allowAssignment)
 {
-  // TODO: Allow other expressions here so that user-defined classes can control
-  // interpolation processing like "tagged template strings" in ES6.
-  loadCoreVariable(compiler, "String");
-
   // Instantiate a new list.
   loadCoreVariable(compiler, "List");
   callMethod(compiler, 0, "new()", 5);
@@ -2224,15 +2230,9 @@ static void stringInterpolation(Compiler* compiler, bool allowAssignment)
     literal(compiler, false);
     callMethod(compiler, 1, "addCore_(_)", 11);
     
+    // The interpolated expression.
     ignoreNewlines(compiler);
-    
-    // Compile the interpolated expression part to a function.
-    Compiler fnCompiler;
-    initCompiler(&fnCompiler, compiler->parser, compiler, true);
-    expression(&fnCompiler);
-    emit(&fnCompiler, CODE_RETURN);
-    endCompiler(&fnCompiler, "interpolation", 9);
-    
+    expression(compiler);
     callMethod(compiler, 1, "addCore_(_)", 11);
     
     ignoreNewlines(compiler);
@@ -2243,8 +2243,8 @@ static void stringInterpolation(Compiler* compiler, bool allowAssignment)
   literal(compiler, false);
   callMethod(compiler, 1, "addCore_(_)", 11);
   
-  // Call .interpolate() with the list of interpolation parts.
-  callMethod(compiler, 1, "interpolate_(_)", 15);
+  // The list of interpolated parts.
+  callMethod(compiler, 0, "join()", 6);
 }
 
 static void super_(Compiler* compiler, bool allowAssignment)
diff --git a/src/vm/wren_core.wren b/src/vm/wren_core.wren
index 303bcb52..e88808cf 100644
--- a/src/vm/wren_core.wren
+++ b/src/vm/wren_core.wren
@@ -131,19 +131,6 @@ class WhereSequence is Sequence {
 class String is Sequence {
   bytes { StringByteSequence.new(this) }
   codePoints { StringCodePointSequence.new(this) }
-
-  static interpolate_(parts) {
-    var result = ""
-    for (part in parts) {
-      if (part is String) {
-        result = result + part
-      } else {
-        result = result + part.call().toString
-      }
-    }
-
-    return result
-  }
 }
 
 class StringByteSequence is Sequence {
diff --git a/src/vm/wren_core.wren.inc b/src/vm/wren_core.wren.inc
index d8f97f2f..4c420683 100644
--- a/src/vm/wren_core.wren.inc
+++ b/src/vm/wren_core.wren.inc
@@ -133,19 +133,6 @@ static const char* coreModuleSource =
 "class String is Sequence {\n"
 "  bytes { StringByteSequence.new(this) }\n"
 "  codePoints { StringCodePointSequence.new(this) }\n"
-"\n"
-"  static interpolate_(parts) {\n"
-"    var result = \"\"\n"
-"    for (part in parts) {\n"
-"      if (part is String) {\n"
-"        result = result + part\n"
-"      } else {\n"
-"        result = result + part.call().toString\n"
-"      }\n"
-"    }\n"
-"\n"
-"    return result\n"
-"  }\n"
 "}\n"
 "\n"
 "class StringByteSequence is Sequence {\n"