diff --git a/test/test_libFLAC++.sh b/test/test_libFLAC++.sh
index 18ddd53b..54205977 100755
--- a/test/test_libFLAC++.sh
+++ b/test/test_libFLAC++.sh
@@ -36,7 +36,7 @@ LD_LIBRARY_PATH=../src/share/replaygain_analysis/.libs:$LD_LIBRARY_PATH
 LD_LIBRARY_PATH=../obj/$BUILD/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH
 export MALLOC_CHECK_=3
-export MALLOC_PERTURB_=$(($RANDOM % 255 + 1))
+export MALLOC_PERTURB_=$((RANDOM % 255 + 1))
 PATH=../src/test_libFLAC++:$PATH
 PATH=../obj/$BUILD/bin:$PATH
 
diff --git a/test/test_libFLAC.sh b/test/test_libFLAC.sh
index 067b4e1f..990ad77c 100755
--- a/test/test_libFLAC.sh
+++ b/test/test_libFLAC.sh
@@ -35,7 +35,7 @@ LD_LIBRARY_PATH=../src/share/replaygain_analysis/.libs:$LD_LIBRARY_PATH
 LD_LIBRARY_PATH=../obj/$BUILD/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH
 export MALLOC_CHECK_=3
-export MALLOC_PERTURB_=$(($RANDOM % 255 + 1))
+export MALLOC_PERTURB_=$((RANDOM % 255 + 1))
 
 PATH=../src/test_libFLAC:$PATH
 PATH=../obj/$BUILD/bin:$PATH
diff --git a/test/test_seeking.sh b/test/test_seeking.sh
index 86e828b4..14c7c2eb 100755
--- a/test/test_seeking.sh
+++ b/test/test_seeking.sh
@@ -33,7 +33,7 @@ LD_LIBRARY_PATH=../src/libFLAC/.libs:$LD_LIBRARY_PATH
 LD_LIBRARY_PATH=../obj/$BUILD/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH
 export MALLOC_CHECK_=3
-export MALLOC_PERTURB_=$(($RANDOM % 255 + 1))
+export MALLOC_PERTURB_=$((RANDOM % 255 + 1))
 PATH=../src/flac:$PATH
 PATH=../src/metaflac:$PATH
 PATH=../src/test_seeking:$PATH
diff --git a/test/test_streams.sh b/test/test_streams.sh
index b5680c41..aa135115 100755
--- a/test/test_streams.sh
+++ b/test/test_streams.sh
@@ -32,7 +32,7 @@ fi
 LD_LIBRARY_PATH=../obj/$BUILD/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH
 export MALLOC_CHECK_=3
-export MALLOC_PERTURB_=$(($RANDOM % 255 + 1))
+export MALLOC_PERTURB_=$((RANDOM % 255 + 1))
 PATH=../src/flac:$PATH
 PATH=../src/test_streams:$PATH
 PATH=../obj/$BUILD/bin:$PATH