diff --git a/compiler/systems.pas b/compiler/systems.pas
index 1f42b643a4..6afc71c725 100644
--- a/compiler/systems.pas
+++ b/compiler/systems.pas
@@ -85,7 +85,7 @@ interface
           id          : tasm;
           idtxt       : string[12];
           asmbin      : string[16];
-          asmcmd      : string[70];
+          asmcmd      : string[100];
           supported_targets : set of tsystem;
           flags        : set of tasmflags;
           labelprefix : string[3];
diff --git a/compiler/wasm32/agllvmmc.pas b/compiler/wasm32/agllvmmc.pas
index 660b0b2c8f..726555cce7 100644
--- a/compiler/wasm32/agllvmmc.pas
+++ b/compiler/wasm32/agllvmmc.pas
@@ -329,7 +329,7 @@ implementation
          id     : as_wasm32_llvm_mc;
          idtxt  : 'LLVM-MC';
          asmbin : 'llvm-mc';
-         asmcmd : '--assemble --arch=wasm32 --filetype=obj -o $OBJ $EXTRAOPT $ASM';
+         asmcmd : '--assemble --arch=wasm32 -mattr=+sign-ext --filetype=obj -o $OBJ $EXTRAOPT $ASM';
          supported_targets : [system_wasm32_wasm,system_wasm32_wasi];
          flags : [];
          labelprefix : '.L';