diff --git a/vertexai/rag/utils/_gapic_utils.py b/vertexai/rag/utils/_gapic_utils.py
index 3ee39a7a0f..0104df41f8 100644
--- a/vertexai/rag/utils/_gapic_utils.py
+++ b/vertexai/rag/utils/_gapic_utils.py
@@ -67,7 +67,7 @@
 )
 
 
-_VALID_RESOURCE_NAME_REGEX = "[a-z][a-zA-Z0-9._-]{0,127}"
+_VALID_RESOURCE_NAME_REGEX = "[a-zA-Z0-9][a-zA-Z0-9._-]{0,127}"
 _VALID_DOCUMENT_AI_PROCESSOR_NAME_REGEX = (
     r"projects/[^/]+/locations/[^/]+/processors/[^/]+(?:/processorVersions/[^/]+)?"
 )