diff --git a/src/main/java/org/apache/sling/repoinit/parser/impl/QuotableStringUtil.java b/src/main/java/org/apache/sling/repoinit/parser/impl/QuotableStringUtil.java
index 1c0d327..cf27c2b 100644
--- a/src/main/java/org/apache/sling/repoinit/parser/impl/QuotableStringUtil.java
+++ b/src/main/java/org/apache/sling/repoinit/parser/impl/QuotableStringUtil.java
@@ -24,8 +24,7 @@
 
 public class QuotableStringUtil {
 
-    private static final Pattern REQUIRES_QUOTES = Pattern.compile("[\\s|\\\\]");
-
+    private static final Pattern REQUIRES_NO_QUOTES = Pattern.compile("[a-zA-Z0-9-_\\./:*@]+");
     private QuotableStringUtil() {
         // hidden
     }
@@ -39,8 +38,8 @@
      */
     @NotNull
     public static final String forRepoInitString(@NotNull String string) {
-        return REQUIRES_QUOTES.matcher(string).find() ? "\"" + string + "\""
-                : string;
+        return REQUIRES_NO_QUOTES.matcher(string).matches() ? string :
+            "\"" + string + "\"";
     }
 
     /**
diff --git a/src/main/java/org/apache/sling/repoinit/parser/operations/RegisterNamespace.java b/src/main/java/org/apache/sling/repoinit/parser/operations/RegisterNamespace.java
index 9e6d3e0..2374455 100644
--- a/src/main/java/org/apache/sling/repoinit/parser/operations/RegisterNamespace.java
+++ b/src/main/java/org/apache/sling/repoinit/parser/operations/RegisterNamespace.java
@@ -28,7 +28,7 @@
     
     public RegisterNamespace(String prefix, String uri) {
         this.prefix = prefix;
-        this.uri = uri;
+        this.uri = cleanupQuotedString(uri);
     }
     
     @Override
@@ -46,8 +46,9 @@
 
     @NotNull
     @Override
-    public String asRepoInitString() {
-        return String.format("register namespace ( %s ) %s%n", prefix, uri);
+    public String asRepoInitString()
+    {
+        return String.format("register namespace ( %s ) %s%n", prefix, QuotableStringUtil.forRepoInitString(uri));
     }
 
     @Override
diff --git a/src/test/resources/testcases/test-40-output.txt b/src/test/resources/testcases/test-40-output.txt
index bb28ce4..010275f 100644
--- a/src/test/resources/testcases/test-40-output.txt
+++ b/src/test/resources/testcases/test-40-output.txt
@@ -1,3 +1,3 @@
 RegisterNamespace (foo) uri:some-uri/V/1.0
 RegisterNamespace (prefix_with-other.things) andSimpleURI
-RegisterNamespace (foo2) uri:some-uri/V/1.1/test#
\ No newline at end of file
+RegisterNamespace (foo2) "uri:some-uri/V/1.1/test#"
\ No newline at end of file