diff --git a/changes/http-link-call.md b/changes/http-link-call.md
new file mode 100644
index 00000000..0884052f
--- /dev/null
+++ b/changes/http-link-call.md
@@ -0,0 +1,8 @@
+bump: patch
+type: fix
+**`ludic build` links `http.ll` only into a program that uses `Http.*`.**
+
+The check that added it grepped the IR for `@hs_`, which every program's header declares,
+so the HTTP transport and Foundation were linked into everything. That cost nothing visible
+on macOS and failed the link on Linux, where `ludic build`, `ludic run` and a new project all
+broke in CI. It now looks for a call to `hs_send`.
diff --git a/tools/ludic-cli/build.ludic b/tools/ludic-cli/build.ludic
index be3f4c3d..da363ce5 100644
--- a/tools/ludic-cli/build.ludic
+++ b/tools/ludic-cli/build.ludic
@@ -75,7 +75,10 @@ function gl_link_flags(ll: pointer) -> pointer {
 # then, in both modes, as `ludicc -o` does (selfhost/main.ludic). Without it a Http.*
 # program built through `ludic build` failed to link on every hs_* symbol.
 function http_link_flags(ll: pointer) -> pointer {
-  if not shq(`grep -q "@hs_" {ll}`) { return "" }
+  # a CALL, not the name: every program's header declares the hs_* transport, so grepping
+  # for "@hs_" linked http.ll and Foundation into everything - harmless on macOS, a failed
+  # link on Linux. Only the Http runtime a program actually uses calls hs_send.
+  if not shq(`grep -q "call void @hs_send" {ll}`) { return "" }
   return ` {ludic_home()}runtime/native/http.ll -Wl,-needed_framework,Foundation`
 }