diff --git a/.github/checks/Makefile b/.github/checks/Makefile
index ee373d53d..7fc51d8d4 100644
--- a/.github/checks/Makefile
+++ b/.github/checks/Makefile
@@ -40,4 +40,7 @@ sorted: sorted.sh sorted_codeopt.sh sorted_opcodes.sh
 	@./sorted_codeopt.sh
 	@./sorted_opcodes.sh
 
+checksp: checksp.sh
+	@./checksp.sh
+
 endif
diff --git a/.github/checks/checksp.sh b/.github/checks/checksp.sh
new file mode 100755
index 000000000..f70d92e25
--- /dev/null
+++ b/.github/checks/checksp.sh
@@ -0,0 +1,22 @@
+#! /bin/bash
+OD65_EXE=../bin/od65
+CHECK_PATH=../../libwrk
+
+cd "${CHECK_PATH}" || {
+    echo "error: Directory ${CHECK_PATH} doesn't seem to exist" >&2
+    exit 1
+}
+
+[ -x "${OD65_EXE}" ] || {
+    echo "error: This check requires the od65 executable to be built" >&2
+    exit 1
+}
+
+EXITCODE=0
+find . -name \*.o -print | while read OBJ; do
+    "${OD65_EXE}" --dump-imports "${OBJ}" | grep -q "\"sp\"" && {
+        echo "error: Usage of symbol 'sp' found in module ${OBJ}" >&2
+        EXITCODE=1
+    }
+done
+exit ${EXITCODE}
diff --git a/.github/workflows/build-on-pull-request.yml b/.github/workflows/build-on-pull-request.yml
index af79733cf..b577e4b03 100644
--- a/.github/workflows/build-on-pull-request.yml
+++ b/.github/workflows/build-on-pull-request.yml
@@ -39,6 +39,9 @@ jobs:
       - name: Build the platform libraries.
         shell: bash
         run: make -j2 lib QUIET=1
+      - name: check test that no modules use sp
+        shell: bash
+        run: make -j2 checksp QUIET=1             
       - name: Run the regression tests.
         shell: bash
         run: make -j2 test QUIET=1
diff --git a/Makefile b/Makefile
index 13e965c9e..21c1b3208 100644
--- a/Makefile
+++ b/Makefile
@@ -53,6 +53,10 @@ checkstyle:
 sorted:
 	@$(MAKE) -C .github/checks --no-print-directory $@
 
+# check that no modules use "sp", requires the binaries to be built first
+checksp:
+	@$(MAKE) -C .github/checks --no-print-directory $@
+
 # runs regression tests, requires libtest target libraries
 test:
 	@$(MAKE) -C test                 --no-print-directory $@
diff --git a/asminc/zeropage.inc b/asminc/zeropage.inc
index 5285779ba..2d4b144db 100644
--- a/asminc/zeropage.inc
+++ b/asminc/zeropage.inc
@@ -13,6 +13,12 @@
         .globalzp       tmp1, tmp2, tmp3, tmp4
         .globalzp       regbank
 
+        ; The following symbol is supplied for compatibility reasons only, it
+        ; will get removed in future versions. Using it will cause a linker
+        ; warning.
+        .globalzp       sp
+
+
 ; The size of the register bank
 regbanksize     = 6
 
diff --git a/libsrc/runtime/sp-compat.s b/libsrc/runtime/sp-compat.s
new file mode 100644
index 000000000..797fef47b
--- /dev/null
+++ b/libsrc/runtime/sp-compat.s
@@ -0,0 +1,11 @@
+;
+; Kugelfuhr, 2025-06-26
+;
+; Add "sp" as an alias for "c_sp" so we don't break old code but emit a
+; linker warning if it is used. Added after renaming "sp" to "c_sp".
+;
+
+.include        "zeropage.inc"
+.export         sp := c_sp
+.assert         0, ldwarning, "Symbol 'sp' is deprecated - please use 'c_sp' instead"
+
diff --git a/test/asm/listing/080-sp-compat.s b/test/asm/listing/080-sp-compat.s
new file mode 100644
index 000000000..8c22a71d3
--- /dev/null
+++ b/test/asm/listing/080-sp-compat.s
@@ -0,0 +1,7 @@
+.include "zeropage.inc"
+
+.proc   _func
+        ldy     #0
+        lda     (sp),y
+        rts
+.endproc
diff --git a/test/asm/listing/ref/080-sp-compat.ld65err2-ref b/test/asm/listing/ref/080-sp-compat.ld65err2-ref
new file mode 100644
index 000000000..fe2611088
--- /dev/null
+++ b/test/asm/listing/ref/080-sp-compat.ld65err2-ref
@@ -0,0 +1 @@
+ld65: Warning: runtime/sp-compat.s:10: Symbol 'sp' is deprecated - please use 'c_sp' instead