diff --git a/src/boot.sh b/src/boot.sh
index c27984e..cce22ea 100644
--- a/src/boot.sh
+++ b/src/boot.sh
@@ -40,13 +40,13 @@ BOOT_OPTS+=" -device isa-applesmc,osk=$osk"
 # OVMF
 DEST="$STORAGE/$DEST"
 
-if [ ! -s "$DEST.rom" ] || [ ! -f "$DEST.rom" ]; then
-  [ ! -s "$OVMF/$ROM" ] || [ ! -f "$OVMF/$ROM" ] && error "UEFI boot file ($OVMF/$ROM) not found!" && exit 44
+if [ ! -s "$DEST.rom" || ! -f "$DEST.rom" ]; then
+  [ ! -s "$OVMF/$ROM" || ! -f "$OVMF/$ROM" ] && error "UEFI boot file ($OVMF/$ROM) not found!" && exit 44
   cp "$OVMF/$ROM" "$DEST.rom"
 fi
 
-if [ ! -s "$DEST.vars" ] || [ ! -f "$DEST.vars" ]; then
-  [ ! -s "$OVMF/$VARS" ] || [ ! -f "$OVMF/$VARS" ]&& error "UEFI vars file ($OVMF/$VARS) not found!" && exit 45
+if [ ! -s "$DEST.vars" || ! -f "$DEST.vars" ]; then
+  [ ! -s "$OVMF/$VARS" || ! -f "$OVMF/$VARS" ]&& error "UEFI vars file ($OVMF/$VARS) not found!" && exit 45
   cp "$OVMF/$VARS" "$DEST.vars"
 fi
 
@@ -73,7 +73,7 @@ if [ ! -f "$IMG" ]; then
 
   [ ! -f "$ISO" ] && gzip -dk "$ISO.gz"
 
-  if [ ! -f "$ISO" ] || [ ! -s "$ISO" ]; then
+  if [ ! -f "$ISO" || ! -s "$ISO" ]; then
     error "Could not find image file \"$ISO\"." && exit 10
   fi
 
diff --git a/src/install.sh b/src/install.sh
index 75a8ae5..64bc4a6 100644
--- a/src/install.sh
+++ b/src/install.sh
@@ -57,7 +57,7 @@ function download() {
   downloadLink=$(echo "$info" | grep 'oscdn' | grep 'dmg')
   downloadSession=$(echo "$info" | grep 'expires' | grep 'dmg')
 
-  if [ -z "$downloadLink" ] || [ -z "$downloadSession" ]; then
+  if [ -z "$downloadLink" || -z "$downloadSession" ]; then
 
     local code="99"
     msg="Failed to connect to the Apple servers, reason:"
@@ -201,12 +201,12 @@ generateSerial() {
   local file="$STORAGE/$PROCESS.sn"
   local file2="$STORAGE/$PROCESS.mlb"
 
-  [ -n "$SN" ] && [ -n "$MLB" ] && return 0
+  [ -n "$SN" && -n "$MLB" ] && return 0
   [ -s "$file" ] && SN=$(<"$file")
   [ -s "$file2" ] && MLB=$(<"$file2")
   SN="${SN//[![:print:]]/}"
   MLB="${MLB//[![:print:]]/}"
-  [ -n "$SN" ] && [ -n "$MLB" ] && return 0
+  [ -n "$SN" && -n "$MLB" ] && return 0
 
   # Generate unique serial numbers for machine
   SN=$(/usr/local/bin/macserial --num 1 --model "${MODEL}" 2>/dev/null)
@@ -238,12 +238,12 @@ if [ -z "$VERSION" ]; then
 
 fi
 
-if [ ! -f "$BASE_IMG" ] || [ ! -s "$BASE_IMG" ]; then
+if [ ! -f "$BASE_IMG" || ! -s "$BASE_IMG" ]; then
 
   STORAGE="$STORAGE/${VERSION,,}"
   BASE_IMG="$STORAGE/base.dmg"
 
-  if [ ! -f "$BASE_IMG" ] || [ ! -s "$BASE_IMG" ]; then
+  if [ ! -f "$BASE_IMG" || ! -s "$BASE_IMG" ]; then
     ! install "$VERSION" "$BASE_IMG" && exit 34
   fi