diff --git a/debug_ebitendebug.go b/debug_ebitendebug.go
new file mode 100644
index 000000000..c10b9882e
--- /dev/null
+++ b/debug_ebitendebug.go
@@ -0,0 +1,21 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build ebitendebug
+
+package ebiten
+
+func isDebug() bool {
+	return true
+}
diff --git a/debug_notebitendebug.go b/debug_notebitendebug.go
new file mode 100644
index 000000000..65ce26660
--- /dev/null
+++ b/debug_notebitendebug.go
@@ -0,0 +1,21 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !ebitendebug
+
+package ebiten
+
+func isDebug() bool {
+	return false
+}
diff --git a/doc.go b/doc.go
index 8df43efd5..7b874a073 100644
--- a/doc.go
+++ b/doc.go
@@ -43,5 +43,6 @@
 // by pressing Q key.
 //
 // The EBITEN_INTERNAL_IMAGES_KEY environment variable specifies the key
-// to dump all the internal images.
+// to dump all the internal images. This is valid only when the build tag
+// 'ebitendebug' is specified.
 package ebiten
diff --git a/run.go b/run.go
index fff07362e..3bdbf98db 100644
--- a/run.go
+++ b/run.go
@@ -109,6 +109,11 @@ type imageDumper struct {
 }
 
 func (i *imageDumper) update(screen *Image) error {
+	const (
+		envScreenshotKey     = "EBITEN_SCREENSHOT_KEY"
+		envInternalImagesKey = "EBITEN_INTERNAL_IMAGES_KEY"
+	)
+
 	if err := i.f(screen); err != nil {
 		return err
 	}
@@ -117,16 +122,21 @@ func (i *imageDumper) update(screen *Image) error {
 	if i.keyState == nil {
 		i.keyState = map[Key]int{}
 
-		if keyname := os.Getenv("EBITEN_SCREENSHOT_KEY"); keyname != "" {
+		if keyname := os.Getenv(envScreenshotKey); keyname != "" {
 			if key, ok := keyNameToKey(keyname); ok {
 				i.hasScreenshotKey = true
 				i.screenshotKey = key
 			}
 		}
-		if keyname := os.Getenv("EBITEN_INTERNAL_IMAGES_KEY"); keyname != "" {
-			if key, ok := keyNameToKey(keyname); ok {
-				i.hasDumpInternalImagesKey = true
-				i.dumpInternalImagesKey = key
+
+		if keyname := os.Getenv(envInternalImagesKey); keyname != "" {
+			if isDebug() {
+				if key, ok := keyNameToKey(keyname); ok {
+					i.hasDumpInternalImagesKey = true
+					i.dumpInternalImagesKey = key
+				}
+			} else {
+				fmt.Fprintf(os.Stderr, "%s is disabled. Specify a build tag 'ebitendebug' to enable it.\n", envInternalImagesKey)
 			}
 		}
 	}