diff --git a/logback.spec b/logback.spec
index 91bbb17..c5bbf23 100644
--- a/logback.spec
+++ b/logback.spec
@@ -119,7 +119,7 @@ rm -r %{name}-*/src/test/java/*
 %build
 
 %{mvn_build} -f -- \
-    -Dproject.build.outputTimestamp=$(date -u -d @${SOURCE_DATE_EPOCH:-$(date +%%s)} +%%Y-%%m-%%dT%%H:%%M:%%SZ)
+    -Dproject.build.outputTimestamp=$(date -u -d @${SOURCE_DATE_EPOCH:-$(date +%%s)} +%%Y-%%m-%%dT%%H:%%M:%%SZ) \
 %if %{?pkg_vcmp:%pkg_vcmp java-devel >= 9}%{!?pkg_vcmp:0}
     -Dmaven.compiler.release=8 \
 %endif