diff --git a/codecs/imagequant/build.sh b/codecs/imagequant/build.sh
index 26f02540..a1ba5115 100755
--- a/codecs/imagequant/build.sh
+++ b/codecs/imagequant/build.sh
@@ -14,6 +14,7 @@ echo "============================================="
   emcc \
     --bind \
     ${OPTIMIZE} \
+    --closure 1 \
     -s ALLOW_MEMORY_GROWTH=1 \
     -s MODULARIZE=1 \
     -s 'EXPORT_NAME="imagequant"' \
@@ -29,6 +30,7 @@ echo "============================================="
   emcc \
     --bind \
     ${OPTIMIZE} \
+    --closure 1 \
     -s ALLOW_MEMORY_GROWTH=1 \
     -s MODULARIZE=1 \
     -s 'EXPORT_NAME="imagequant"' \
diff --git a/codecs/mozjpeg_enc/build.sh b/codecs/mozjpeg_enc/build.sh
index c4936861..668c4d1d 100755
--- a/codecs/mozjpeg_enc/build.sh
+++ b/codecs/mozjpeg_enc/build.sh
@@ -30,6 +30,7 @@ echo "============================================="
   emcc \
     --bind \
     ${OPTIMIZE} \
+    --closure 1 \
     -s WASM=1 \
     -s ALLOW_MEMORY_GROWTH=1 \
     -s MODULARIZE=1 \
diff --git a/codecs/webp_dec/build.sh b/codecs/webp_dec/build.sh
index dc71e5a5..c630dad7 100755
--- a/codecs/webp_dec/build.sh
+++ b/codecs/webp_dec/build.sh
@@ -39,6 +39,7 @@ echo "============================================="
 (
   emcc \
     ${OPTIMIZE} \
+    --closure 1 \
     --bind \
     -s ALLOW_MEMORY_GROWTH=1 \
     -s MODULARIZE=1 \
diff --git a/codecs/webp_enc/build.sh b/codecs/webp_enc/build.sh
index 79ac0b5d..36fe8dc4 100755
--- a/codecs/webp_enc/build.sh
+++ b/codecs/webp_enc/build.sh
@@ -40,6 +40,7 @@ echo "============================================="
 (
   emcc \
     ${OPTIMIZE} \
+    --closure 1 \
     --bind \
     -s ALLOW_MEMORY_GROWTH=1 \
     -s MODULARIZE=1 \