diff --git a/artiq/compiler/transforms/llvm_ir_generator.py b/artiq/compiler/transforms/llvm_ir_generator.py
index 197bc2cdf..7bf6037f8 100644
--- a/artiq/compiler/transforms/llvm_ir_generator.py
+++ b/artiq/compiler/transforms/llvm_ir_generator.py
@@ -1359,11 +1359,24 @@ class LLVMIRGenerator:
         else:
             llfun = self.map(insn.static_target_function)
         llenv     = self.llbuilder.extract_value(llclosure, 0, name="env.fun")
-        return llfun, [llenv] + list(llargs), {}
+        return llfun, [llenv] + list(llargs), {}, None
 
     def _prepare_ffi_call(self, insn):
         llargs = []
         llarg_attrs = {}
+
+        stack_save_needed = False
+        for i, arg in enumerate(insn.arguments()):
+            llarg = self.map(arg)            
+            if isinstance(llarg.type, (ll.LiteralStructType, ll.IdentifiedStructType)):
+                stack_save_needed = True
+                break
+
+        if stack_save_needed:
+            llcallstackptr = self.llbuilder.call(self.llbuiltin("llvm.stacksave"), [])
+        else:
+            llcallstackptr = None
+
         for i, arg in enumerate(insn.arguments()):
             llarg = self.map(arg)
             if isinstance(llarg.type, (ll.LiteralStructType, ll.IdentifiedStructType)):
@@ -1399,7 +1412,7 @@ class LLVMIRGenerator:
             if 'nowrite' in insn.target_function().type.flags:
                 llfun.attributes.add('inaccessiblememonly')
 
-        return llfun, list(llargs), llarg_attrs
+        return llfun, list(llargs), llarg_attrs, llcallstackptr
 
     def _build_rpc(self, fun_loc, fun_type, args, llnormalblock, llunwindblock):
         llservice = ll.Constant(lli32, fun_type.service)
@@ -1535,9 +1548,9 @@ class LLVMIRGenerator:
                                    insn.arguments(),
                                    llnormalblock=None, llunwindblock=None)
         elif types.is_external_function(functiontyp):
-            llfun, llargs, llarg_attrs = self._prepare_ffi_call(insn)
+            llfun, llargs, llarg_attrs, llcallstackptr = self._prepare_ffi_call(insn)
         else:
-            llfun, llargs, llarg_attrs = self._prepare_closure_call(insn)
+            llfun, llargs, llarg_attrs, llcallstackptr = self._prepare_closure_call(insn)
 
         if self.has_sret(functiontyp):
             llstackptr = self.llbuilder.call(self.llbuiltin("llvm.stacksave"), [])
@@ -1556,6 +1569,9 @@ class LLVMIRGenerator:
                 # {} elsewhere.
                 llresult = ll.Constant(llunit, [])
 
+        if llcallstackptr != None:
+            self.llbuilder.call(self.llbuiltin("llvm.stackrestore"), [llcallstackptr])
+
         return llresult
 
     def process_Invoke(self, insn):