diff --git a/scripts/common.sh b/scripts/common.sh
index fbb730241..797510d33 100644
--- a/scripts/common.sh
+++ b/scripts/common.sh
@@ -37,21 +37,21 @@ safe_kill()
     local n=1
 
     # only proceed if $PID does exist
-    kill -0 $PID 2>/dev/null || return
+    kill -0 "$PID" 2>/dev/null || return
 
     echo "Sending SIGTERM to ${NAME} (${PID}) ..."
-    kill $PID
+    kill "$PID"
 
     # wait until process terminated gracefully
-    while kill -0 $PID 2>/dev/null && [[ $n -le 4 ]]; do
+    while kill -0 "$PID" 2>/dev/null && [[ $n -le 4 ]]; do
         echo "Waiting ($n) ..."
         sleep 1
         n=$[n + 1]
     done
 
     # process still alive? then hard-kill
-    if kill -0 $PID 2>/dev/null; then
+    if kill -0 "$PID" 2>/dev/null; then
         echo "Sending SIGKILL to ${NAME} (${PID}) ..."
-        kill -9 $PID
+        kill -9 "$PID"
     fi
 }
diff --git a/test/externalTests.sh b/test/externalTests.sh
index 7bf3eb76b..e53f9925a 100755
--- a/test/externalTests.sh
+++ b/test/externalTests.sh
@@ -42,10 +42,10 @@ source test/externalTests/common.sh
 
 printTask "Running external tests..."
 
-$REPO_ROOT/externalTests/zeppelin.sh "$SOLJSON"
-$REPO_ROOT/externalTests/gnosis.sh "$SOLJSON"
-$REPO_ROOT/externalTests/colony.sh "$SOLJSON"
-$REPO_ROOT/externalTests/ens.sh "$SOLJSON"
+"$REPO_ROOT/externalTests/zeppelin.sh" "$SOLJSON"
+"$REPO_ROOT/externalTests/gnosis.sh" "$SOLJSON"
+"$REPO_ROOT/externalTests/colony.sh" "$SOLJSON"
+"$REPO_ROOT/externalTests/ens.sh" "$SOLJSON"
 
 # Disabled temporarily as it needs to be updated to latest Truffle first.
 #test_truffle Gnosis https://github.com/axic/pm-contracts.git solidity-050
diff --git a/test/externalTests/solc-js/solc-js.sh b/test/externalTests/solc-js/solc-js.sh
index db01a2ae7..fd59c4398 100755
--- a/test/externalTests/solc-js/solc-js.sh
+++ b/test/externalTests/solc-js/solc-js.sh
@@ -41,10 +41,10 @@ function solcjs_test
     echo "require('./determinism.js');" >> test/index.js
 
     printLog "Copying determinism.js..."
-    cp -f $SOLCJS_INPUT_DIR/determinism.js test/
+    cp -f "$SOLCJS_INPUT_DIR/determinism.js" test/
 
     printLog "Copying contracts..."
-    cp -Rf $SOLCJS_INPUT_DIR/DAO test/
+    cp -Rf "$SOLCJS_INPUT_DIR/DAO" test/
 
     printLog "Copying SMTChecker tests..."
     cp -Rf "$TEST_DIR"/test/libsolidity/smtCheckerTests test/
@@ -52,7 +52,7 @@ function solcjs_test
 
     # Update version (needed for some tests)
     echo "Updating package.json to version $VERSION"
-    npm version --allow-same-version --no-git-tag-version $VERSION
+    npm version --allow-same-version --no-git-tag-version "$VERSION"
 
     run_test compile_fn test_fn
 }