diff --git a/ChangeLog b/ChangeLog
index 78bcc0f..46230ac 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -39,6 +39,8 @@ assertion could always be wrapped in a repeated group. The only restriction
 that is now imposed is that an unlimited maximum is changed to one more than 
 the minimum.
 
+10. Fix *THEN verbs in lookahead assertions in JIT.
+
 
 Version 10.34 21-November-2019
 ------------------------------
diff --git a/src/pcre2_jit_compile.c b/src/pcre2_jit_compile.c
index 78b94c1..00d13f1 100644
--- a/src/pcre2_jit_compile.c
+++ b/src/pcre2_jit_compile.c
@@ -9597,7 +9597,8 @@ if (opcode == OP_ASSERT || opcode == OP_ASSERTBACK)
         }
       else
         {
-        OP1(SLJIT_MOV, STR_PTR, 0, SLJIT_MEM1(STACK_TOP), 0);
+        SLJIT_ASSERT(extrasize == 3);
+        OP1(SLJIT_MOV, STR_PTR, 0, SLJIT_MEM1(STACK_TOP), STACK(-1));
         OP1(SLJIT_MOV, SLJIT_MEM1(STACK_TOP), STACK(0), bra == OP_BRAZERO ? STR_PTR : SLJIT_IMM, 0);
         }
       }
diff --git a/src/pcre2_jit_test.c b/src/pcre2_jit_test.c
index e0638ef..a188724 100644
--- a/src/pcre2_jit_test.c
+++ b/src/pcre2_jit_test.c
@@ -860,6 +860,7 @@ static struct regression_test_case regression_test_cases[] = {
 	{ MU, A, 0, 0, "(?(?!a(*THEN)b)ad|add)", "add" },
 	{ MU, A, 0, 0 | F_NOMATCH, "(?(?=a)a(*THEN)b|ad)", "ad" },
 	{ MU, A, 0, 0, "(?!(?(?=a)ab|b(*THEN)d))bn|bnn", "bnn" },
+	{ MU, A, 0, 0, "(?=(*THEN: ))* ", " " },
 
 	/* Recurse and control verbs. */
 	{ MU, A, 0, 0, "(a(*ACCEPT)b){0}a(?1)b", "aacaabb" },