diff --git a/run_tests.sh b/run_tests.sh
index d27a2dc7..9b080e19 100755
--- a/run_tests.sh
+++ b/run_tests.sh
@@ -52,8 +52,8 @@ for arg in "$@"; do
   process_option $arg
 done
 
+# If enabled, tell nose to collect coverage data 
 if [ $coverage -eq 1 ]; then
-    ${wrapper} coverage erase
     noseopts="$noseopts --with-coverage --cover-package=nova"
 fi
 
@@ -116,6 +116,11 @@ then
   fi
 fi
 
+# Delete old coverage data from previous runs
+if [ $coverage -eq 1 ]; then
+    ${wrapper} coverage erase
+fi
+
 if [ $just_pep8 -eq 1 ]; then
     run_pep8
     exit