diff --git a/Makefile b/Makefile
index c1becbc99..b115078c4 100644
--- a/Makefile
+++ b/Makefile
@@ -70,8 +70,8 @@ $(GENERATED_CRDS): $(GENERATED)
 	@rm manifests/acid.zalan.do_operatorconfigurations.yaml
 	@mv manifests/acid.zalan.do_postgresqls.yaml manifests/postgresql.crd.yaml
 	@# hack to use lowercase kind and listKind
-	@sed -i -e 's/kind: Postgresql/kind: postgresql/' manifests/postgresql.crd.yaml
-	@sed -i -e 's/listKind: PostgresqlList/listKind: postgresqlList/' manifests/postgresql.crd.yaml
+	@sed -i '' -e 's/kind: Postgresql/kind: postgresql/' manifests/postgresql.crd.yaml
+	@sed -i '' -e 's/listKind: PostgresqlList/listKind: postgresqlList/' manifests/postgresql.crd.yaml
 	@hack/adjust_postgresql_crd.sh
 	@mv manifests/acid.zalan.do_postgresteams.yaml manifests/postgresteam.crd.yaml
 	@cp manifests/postgresql.crd.yaml pkg/apis/acid.zalan.do/v1/postgresql.crd.yaml
diff --git a/hack/adjust_postgresql_crd.sh b/hack/adjust_postgresql_crd.sh
index d06b74a2d..ff111b621 100755
--- a/hack/adjust_postgresql_crd.sh
+++ b/hack/adjust_postgresql_crd.sh
@@ -13,12 +13,12 @@
 
 file="${1:-"manifests/postgresql.crd.yaml"}"
 
-sed -i '/^[[:space:]]*standby:$/{
+sed -i '' '/^[[:space:]]*standby:$/{
     # Capture the indentation
     s/^\([[:space:]]*\)standby:$/\1standby:\n\1  anyOf:\n\1  - required:\n\1    - s3_wal_path\n\1  - required:\n\1    - gs_wal_path\n\1  - required:\n\1    - standby_host\n\1  not:\n\1    required:\n\1    - s3_wal_path\n\1    - gs_wal_path/
 }' "$file"
 
-sed -i '/^[[:space:]]*maintenanceWindows:$/{
+sed -i '' '/^[[:space:]]*maintenanceWindows:$/{
     # Capture the indentation
     s/^\([[:space:]]*\)maintenanceWindows:$/\1maintenanceWindows:\n\1  items:\n\1    pattern: '\''^\\ *((Mon|Tue|Wed|Thu|Fri|Sat|Sun):(2[0-3]|[01]?\\d):([0-5]?\\d)|(2[0-3]|[01]?\\d):([0-5]?\\d))-((2[0-3]|[01]?\\d):([0-5]?\\d)|(2[0-3]|[01]?\\d):([0-5]?\\d))\\ *$'\''\n\1    type: string/
 }' "$file"