diff --git a/xml/xml-analysis-impl/src/com/intellij/xml/util/XmlRefCountHolder.java b/xml/xml-analysis-impl/src/com/intellij/xml/util/XmlRefCountHolder.java
index aa7518656f0b..7671b6fe7112 100644
--- a/xml/xml-analysis-impl/src/com/intellij/xml/util/XmlRefCountHolder.java
+++ b/xml/xml-analysis-impl/src/com/intellij/xml/util/XmlRefCountHolder.java
@@ -71,7 +71,7 @@ public class XmlRefCountHolder {
   private final Set<String> myUsedPrefixes = new HashSet<>();
   private final Set<String> myUsedNamespaces = new HashSet<>();
 
-  private static final Pattern PREFIX_PATTERN = Pattern.compile("\\w+:");
+  private static final Pattern PREFIX_PATTERN = Pattern.compile("[\\w_][\\w_.]*:");
 
   @Nullable
   public static XmlRefCountHolder getRefCountHolder(@NotNull XmlFile file) {