diff --git a/install.sh b/install.sh
index cfee8d0..9b4b488 100755
--- a/install.sh
+++ b/install.sh
@@ -21,14 +21,26 @@ chmod 700 "$BIN_DIR/gori-agent"
 
 PATH_BLOCK_START="# >>> gori-agent >>>"
 PATH_BLOCK_END="# <<< gori-agent <<<"
-if [[ -w "$PROFILE_FILE" ]] && ! grep -q "$PATH_BLOCK_START" "$PROFILE_FILE"; then
+if [[ -w "$PROFILE_FILE" ]]; then
+  PROFILE_TEMP="$(mktemp "${PROFILE_FILE}.gori-agent.XXXXXX")"
+  if ! awk -v start="$PATH_BLOCK_START" -v end="$PATH_BLOCK_END" '
+    $0 == start { if (skipping) exit 2; skipping = 1; next }
+    $0 == end { if (!skipping) exit 2; skipping = 0; next }
+    !skipping { print }
+    END { if (skipping) exit 2 }
+  ' "$PROFILE_FILE" >"$PROFILE_TEMP"; then
+    rm -f "$PROFILE_TEMP"
+    echo "Malformed gori-agent block in $PROFILE_FILE" >&2
+    exit 1
+  fi
   {
-    echo ""
     echo "$PATH_BLOCK_START"
     echo "export GORI_AGENT_ROOT=\"$GORI_AGENT_ROOT\""
     echo "export PATH=\"$BIN_DIR:\$PATH\""
     echo "$PATH_BLOCK_END"
-  } >>"$PROFILE_FILE"
+  } >>"$PROFILE_TEMP"
+  chmod --reference="$PROFILE_FILE" "$PROFILE_TEMP"
+  mv "$PROFILE_TEMP" "$PROFILE_FILE"
 fi
 
 echo "Installed gori-agent to $BIN_DIR/gori-agent"