diff --git a/tests/qemu-iotests/common.config b/tests/qemu-iotests/common.config
index d5a72affc642225b0611d5ac2c682d0b004b992e..d07f43569638fbeeda2c9cf7faf444ded0acadd0 100644
--- a/tests/qemu-iotests/common.config
+++ b/tests/qemu-iotests/common.config
@@ -87,13 +87,19 @@ export BC_PROG="`set_prog_path bc`"
 
 export PS_ALL_FLAGS="-ef"
 
-export QEMU_PROG="`set_prog_path qemu`"
+if [ -z "$QEMU_PROG" ]; then
+    export QEMU_PROG="`set_prog_path qemu`"
+fi
 [ "$QEMU_PROG" = "" ] && _fatal "qemu not found"
 
-export QEMU_IMG_PROG="`set_prog_path qemu-img`"
+if [ -z "$QEMU_IMG_PROG" ]; then
+    export QEMU_IMG_PROG="`set_prog_path qemu-img`"
+fi
 [ "$QEMU_IMG_PROG" = "" ] && _fatal "qemu-img not found"
 
-export QEMU_IO_PROG="`set_prog_path qemu-io`"
+if [ -z "$QEMU_IO_PROG" ]; then
+    export QEMU_IO_PROG="`set_prog_path qemu-io`"
+fi
 [ "$QEMU_IO_PROG" = "" ] && _fatal "qemu-io not found"
 
 export QEMU=$QEMU_PROG