diff --git a/+globalmacrodata/gmd.m b/+globalmacrodata/gmd.m
index b133ba0..7e5fc20 100644
--- a/+globalmacrodata/gmd.m
+++ b/+globalmacrodata/gmd.m
@@ -434,13 +434,7 @@
 end
 
 function out = loadSourceData(srcName, anything, countryArg)
-    csColPrefix = '';
-    name = strtrim(srcName);
-    if numel(name) == 7 && startsWith(name, 'CS')
-        parts = strsplit(name, '_');
-        csColPrefix = parts{1};
-        name = normalizeSourceName(name);
-    end
+    [name, csColPrefix] = normalizeSourceName(srcName);
     srcTokens = tokens(name);
     if numel(srcTokens) > 1
         fail(498, 'Warning: Please specify exactly one source.');
diff --git a/+globalmacrodata/private/normalizeSourceName.m b/+globalmacrodata/private/normalizeSourceName.m
index de87abd..32eb278 100644
--- a/+globalmacrodata/private/normalizeSourceName.m
+++ b/+globalmacrodata/private/normalizeSourceName.m
@@ -1,9 +1,14 @@
-function s = normalizeSourceName(source)
-%NORMALIZESOURCENAME Convert a 7-char CS alias (e.g. "CS1_ARG") to "ARG_1".
-%   Ports the Python _normalize_source_name helper.
+function [s, csPrefix] = normalizeSourceName(source)
+%NORMALIZESOURCENAME Convert a CS alias to its file name.
+%   "CS1_ARG" -> "ARG_1", "CS10_ITA" -> "ITA_10". Also returns the column
+%   prefix inside the file ("CS1", "CS10"), or '' when the name is not a CS
+%   alias. Ports the Python _normalize_source_name helper.
 
     s = strtrim(char(source));
-    if numel(s) == 7 && startsWith(s, 'CS')
-        s = sprintf('%s_%s', s(end-2:end), s(3));
+    csPrefix = '';
+    tok = regexp(s, '^CS(\d+)_([A-Za-z]{3})$', 'tokens', 'once', 'ignorecase');
+    if ~isempty(tok)
+        csPrefix = ['CS', tok{1}];
+        s = sprintf('%s_%s', upper(tok{2}), tok{1});
     end
 end
diff --git a/tests/fixtures/clean/combined/ITA_10.dta b/tests/fixtures/clean/combined/ITA_10.dta
new file mode 100644
index 0000000..d1a71c9
Binary files /dev/null and b/tests/fixtures/clean/combined/ITA_10.dta differ
diff --git a/tests/tGmdOffline.m b/tests/tGmdOffline.m
index 68fa983..599b529 100644
--- a/tests/tGmdOffline.m
+++ b/tests/tGmdOffline.m
@@ -121,6 +121,44 @@ function sourceCsAliasResolves(tc)
             tc.verifyTrue(ismember('CS1_M3_GDP', df.Properties.VariableNames));
         end
 
+        function sourceCsAliasTwoDigitSlot(tc)
+            % CS10_ITA normalizes to source ITA_10 with data columns prefixed CS10_.
+            df = globalmacrodata.gmd('sources','CS10_ITA','variables','CPI');
+            tc.verifyEqual(df.Properties.VariableNames, {'ISO3','year','CS10_CPI'});
+            tc.verifyEqual(height(df), 10);
+        end
+
+        function sourceCsAliasIgnoresCase(tc)
+            df = globalmacrodata.gmd('sources','cs10_ita');
+            tc.verifyTrue(ismember('CS10_rGDP', df.Properties.VariableNames));
+        end
+
+        function sourceCsAliasTrimsWhitespace(tc)
+            df = globalmacrodata.gmd('sources',' CS10_ITA ','variables','CPI');
+            tc.verifyEqual(df.Properties.VariableNames, {'ISO3','year','CS10_CPI'});
+        end
+
+        function sourceCsNearMissNotTranslated(tc)
+            % CS1_ARGX is not a CS alias, so it must not resolve to ARG_1.
+            tc.verifyError(@() globalmacrodata.gmd('sources','CS1_ARGX'), 'GMD:e498');
+        end
+
+        function sourceFileNameLoads(tc)
+            df = globalmacrodata.gmd('sources','ITA_10');
+            tc.verifyTrue(ismember('CS10_CPI', df.Properties.VariableNames));
+        end
+
+        function sourceCsAliasUnknownVariableListsCodes(tc)
+            % The error lists the codes with the CS10_ prefix stripped.
+            try
+                globalmacrodata.gmd('sources','CS10_ITA','variables','M3');
+                tc.verifyFail('Expected error GMD:e498.');
+            catch ME
+                tc.verifyEqual(ME.identifier, 'GMD:e498');
+                tc.verifySubstring(ME.message, 'It has data on CPI nGDP rGDP.');
+            end
+        end
+
         function invalidSourceRaises(tc)
             tc.verifyError(@() globalmacrodata.gmd('sources','NOPE'), 'GMD:e498');
         end