diff --git a/value/src/main/java/com/google/auto/value/processor/builder.vm b/value/src/main/java/com/google/auto/value/processor/builder.vm
index 5b29108bdf..630330cafa 100644
--- a/value/src/main/java/com/google/auto/value/processor/builder.vm
+++ b/value/src/main/java/com/google/auto/value/processor/builder.vm
@@ -239,31 +239,41 @@ class ${builderName}${builderFormalTypes} ##
 #end
 
 #if (!$builderRequiredProperties.empty)
+    if (#foreach ($p in $builderRequiredProperties)##
+        this.$p == null##
+          #if ($foreach.hasNext)
+
+        || #end
+        #end) {
+
   #if ($identifiers)  ## build a friendly message showing all missing properties
+    #if ($builderRequiredProperties.size() == 1)
 
-    `java.lang.String` missing = "";
+    `java.lang.String` missing = " $builderRequiredProperties.iterator().next()";
 
-    #foreach ($p in $builderRequiredProperties)
+    #else
+
+    `java.lang.StringBuilder` missing = new `java.lang.StringBuilder`();
+
+      #foreach ($p in $builderRequiredProperties)
 
     if (this.$p == null) {
-      missing += " $p.name";
+      missing.append(" $p.name");
     }
 
+      #end
     #end
 
-    if (!missing.isEmpty()) {
-      throw new IllegalStateException("Missing required properties:" + missing);
-    }
+    throw new IllegalStateException("Missing required properties:" + missing);
 
   #else  ## just throw an exception if anything is missing
 
-    if (#foreach ($p in $builderRequiredProperties)##
-        this.$p == null##
-        #if ($foreach.hasNext) || #end
-        #end) {
-      throw new IllegalStateException();
-    }
+    throw new IllegalStateException();
+
   #end
+
+  }
+
 #end
 
     #if ($builtType != "void") return #end ${build}(
diff --git a/value/src/test/java/com/google/auto/value/processor/AutoBuilderCompilationTest.java b/value/src/test/java/com/google/auto/value/processor/AutoBuilderCompilationTest.java
index ddf12ff3c1..2a5f55a07f 100644
--- a/value/src/test/java/com/google/auto/value/processor/AutoBuilderCompilationTest.java
+++ b/value/src/test/java/com/google/auto/value/processor/AutoBuilderCompilationTest.java
@@ -58,14 +58,15 @@ public final class AutoBuilderCompilationTest {
           "",
           "  @Override",
           "  public Baz build() {",
-          "    String missing = \"\";",
-          "    if (this.anInt == null) {",
-          "      missing += \" anInt\";",
-          "    }",
-          "    if (this.aString == null) {",
-          "      missing += \" aString\";",
-          "    }",
-          "    if (!missing.isEmpty()) {",
+          "    if (this.anInt == null",
+          "        || this.aString == null) {",
+          "      StringBuilder missing = new StringBuilder();",
+          "      if (this.anInt == null) {",
+          "        missing.append(\" anInt\");",
+          "      }",
+          "      if (this.aString == null) {",
+          "        missing.append(\" aString\");",
+          "      }",
           "      throw new IllegalStateException(\"Missing required properties:\" + missing);",
           "    }",
           "    return new Baz(",
diff --git a/value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java b/value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java
index 4d9026ace2..1baf4b4dc2 100644
--- a/value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java
+++ b/value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java
@@ -1311,17 +1311,19 @@ public void correctBuilder() {
                 + "NestedAutoValue.builder();",
             "        this.aNestedAutoValue = aNestedAutoValue$builder.build();",
             "      }",
-            "      String missing = \"\";",
-            "      if (this.anInt == null) {",
-            "        missing += \" anInt\";",
-            "      }",
-            "      if (this.aByteArray == null) {",
-            "        missing += \" aByteArray\";",
-            "      }",
-            "      if (this.aList == null) {",
-            "        missing += \" aList\";",
-            "      }",
-            "      if (!missing.isEmpty()) {",
+            "      if (this.anInt == null",
+            "          || this.aByteArray == null",
+            "          || this.aList == null) {",
+            "        StringBuilder missing = new StringBuilder();",
+            "        if (this.anInt == null) {",
+            "          missing.append(\" anInt\");",
+            "        }",
+            "        if (this.aByteArray == null) {",
+            "          missing.append(\" aByteArray\");",
+            "        }",
+            "        if (this.aList == null) {",
+            "          missing.append(\" aList\");",
+            "        }",
             "        throw new IllegalStateException(\"Missing required properties:\" + missing);",
             "      }",
             "      return new AutoValue_Baz<T>(",