diff --git a/emu/fpu.c b/emu/fpu.c
index dd4b86d4..4b18f8f7 100644
--- a/emu/fpu.c
+++ b/emu/fpu.c
@@ -93,6 +93,14 @@ void fpu_ucom(struct cpu_state *cpu, int i) {
         cpu->c0 = cpu->c2 = cpu->c3 = 1;
 }
 
+void fpu_abs(struct cpu_state *cpu) {
+    ST(0) = f80_abs(ST(0));
+}
+
+void fpu_chs(struct cpu_state *cpu) {
+    ST(0) = f80_neg(ST(0));
+}
+
 void fpu_add(struct cpu_state *cpu, int srci, int dsti) {
     ST(dsti) = f80_add(ST(srci), ST(dsti));
 }
diff --git a/emu/fpu.h b/emu/fpu.h
index 138d8645..0aa01b12 100644
--- a/emu/fpu.h
+++ b/emu/fpu.h
@@ -30,6 +30,8 @@ void fpu_ldm80(struct cpu_state *cpu, float80 *f);
 
 void fpu_prem(struct cpu_state *cpu);
 void fpu_ucom(struct cpu_state *cpu, int i);
+void fpu_abs(struct cpu_state *cpu);
+void fpu_chs(struct cpu_state *cpu);
 
 void fpu_add(struct cpu_state *cpu, int srci, int dsti);
 void fpu_sub(struct cpu_state *cpu, int srci, int dsti);
diff --git a/jit/gen.c b/jit/gen.c
index 53ca014d..5a339d6e 100644
--- a/jit/gen.c
+++ b/jit/gen.c
@@ -339,8 +339,8 @@ static inline bool gen_op(struct gen_state *state, gadget_t *gadgets, enum arg a
 #define FUCOM() hh(fpu_ucom, st_i)
 #define FUCOMI() UNDEFINED
 #define FST() hh(fpu_st, st_i)
-#define FCHS() UNDEFINED
-#define FABS() UNDEFINED
+#define FCHS() h(fpu_chs)
+#define FABS() h(fpu_abs)
 #define FLDC(what) hh(fpu_ldc, fconst_##what)
 #define FPREM() h(fpu_prem)
 #define FSTSW(dst) if (arg_##dst == arg_reg_a) g(fstsw_ax); else UNDEFINED