diff --git a/install.sh b/install.sh
index 3b04f45..9b22969 100755
--- a/install.sh
+++ b/install.sh
@@ -49,24 +49,24 @@ function ensure_file_from_example {
 
 if [ $(ver $DOCKER_VERSION) -lt $(ver $MIN_DOCKER_VERSION) ]; then
     echo "FAIL: Expected minimum Docker version to be $MIN_DOCKER_VERSION but found $DOCKER_VERSION"
-    exit -1
+    exit 1
 fi
 
 if [ $(ver $COMPOSE_VERSION) -lt $(ver $MIN_COMPOSE_VERSION) ]; then
     echo "FAIL: Expected minimum docker-compose version to be $MIN_COMPOSE_VERSION but found $COMPOSE_VERSION"
-    exit -1
+    exit 1
 fi
 
 if [ "$RAM_AVAILABLE_IN_DOCKER" -lt "$MIN_RAM" ]; then
     echo "FAIL: Expected minimum RAM available to Docker to be $MIN_RAM MB but found $RAM_AVAILABLE_IN_DOCKER MB"
-    exit -1
+    exit 1
 fi
 
 #SSE4.2 required by Clickhouse (https://clickhouse.yandex/docs/en/operations/requirements/) 
-SUPPORTS_SSE42=$(docker run --rm busybox grep -c sse4_2 /proc/cpuinfo);
+SUPPORTS_SSE42=$(docker run --rm busybox grep -c sse4_2 /proc/cpuinfo || :);
 if (($SUPPORTS_SSE42 == 0)); then
     echo "FAIL: The CPU your machine is running on does not support the SSE 4.2 instruction set, which is required for one of the services Sentry uses (Clickhouse). See https://git.io/JvLDt for more info."
-    exit -1
+    exit 1
 fi
 
 # Clean up old stuff and ensure nothing is working while we install/update