diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -1920,7 +1920,7 @@
     // Next, check the extension directive map to see if any extension has
     // registered itself to parse this directive.
     std::pair<MCAsmParserExtension *, DirectiveHandler> Handler =
-        ExtensionDirectiveMap.lookup(IDVal);
+        ExtensionDirectiveMap.lookup(IDVal.lower());
     if (Handler.first)
       return (*Handler.second)(Handler.first, IDVal, IDLoc);
 
diff --git a/llvm/test/MC/ELF/elf_directive_section.s b/llvm/test/MC/ELF/elf_directive_section.s
--- a/llvm/test/MC/ELF/elf_directive_section.s
+++ b/llvm/test/MC/ELF/elf_directive_section.s
@@ -21,3 +21,24 @@
 	.tdata
 # CHECK: .tdata
 
+	.BSS
+# CHECK: .bss
+
+	.DATA.REL.RO
+# CHECK: .data.rel.ro
+
+	.DATA.REL
+# CHECK: .data.rel
+
+	.EH_FRAME
+# CHECK: .eh_frame
+
+	.RODATA
+# CHECK: .rodata
+
+	.TBSS
+# CHECK: .tbss
+
+	.TDATA
+# CHECK: .tdata
+