diff --git a/testfiles/pgfmath-gh1123.lvt b/testfiles/pgfmath-gh1123.lvt
new file mode 100644
index 000000000..0bb7f1f92
--- /dev/null
+++ b/testfiles/pgfmath-gh1123.lvt
@@ -0,0 +1,33 @@
+\documentclass{minimal}
+\input{pgf-regression-test}
+
+\RequirePackage{pgfmath}
+
+\makeatletter
+\csname protected\endcsname\long\def\ASSERTPGFMATHFUNCTIONS#1#2{%
+  \pgfexpl@tl@if@eq@@ccTF{pgfmath#1@}{pgfmath#2@}{%
+    \TYPE{PASSED}%
+    \TYPE{\pgfexpl@cs@meaning@@c{pgfmath#1@}}%
+  }{%
+    \TYPE{FAILED}%
+    \TYPE{\pgfexpl@cs@meaning@@c{pgfmath#1@}}%
+    \TYPE{\pgfexpl@cs@meaning@@c{pgfmath#2@}}%
+  }%
+}
+\makeatother
+
+\START
+
+\BEGINTEST{/pgf/declare function, space(s) in arg list}
+  \pgfkeys{
+    /pgf/declare function={
+      funcA( \x,\y) = sqrt(\x^2 + \y^2);
+      funcB( \x, \y) = sqrt(\x^2 + \y^2);
+      funcX(\x,\y) = sqrt(\x^2 + \y^2);
+    }
+  }
+  \ASSERTPGFMATHFUNCTIONS{funcA}{funcX}
+  \ASSERTPGFMATHFUNCTIONS{funcB}{funcX}
+\ENDTEST
+
+\END
diff --git a/testfiles/pgfmath-gh1123.tlg b/testfiles/pgfmath-gh1123.tlg
new file mode 100644
index 000000000..ed5de0783
--- /dev/null
+++ b/testfiles/pgfmath-gh1123.tlg
@@ -0,0 +1,10 @@
+This is a generated file for the l3build validation system.
+Don't change this file in any respect.
+============================================================
+TEST 1: /pgf/declare function, space(s) in arg list
+============================================================
+PASSED
+macro:#1#2->\pgfmathparse {sqrt(#1^2+#2^2)}
+PASSED
+macro:#1#2->\pgfmathparse {sqrt(#1^2+#2^2)}
+============================================================