diff --git a/src/test/data/script_tests.json b/src/test/data/script_tests.json
--- a/src/test/data/script_tests.json
+++ b/src/test/data/script_tests.json
@@ -897,8 +897,18 @@
 ["-42 521", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "PUSH_SIZE", "Pushing 521 bytes is not"],
 ["-42 -3", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "PUSH_SIZE", "Negative size"],
 ["0x05 0xabcdef4280 4", "NUM2BIN 0x04 0xabcdefc2 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "Item size reduction"],
+["0x03 0xabcdef 2", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "IMPOSSIBLE_ENCODING", "output too small"],
+["0x03 0xabcdef 3", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK"],
 ["0x01 0x80 0", "NUM2BIN 0 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "Negative zero"],
 ["0x01 0x80 3", "NUM2BIN 0x03 0x000000 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "Negative zero, larger output"],
+["0x05 0xabcdef4243 5", "NUM2BIN 0x05 0xabcdef4243 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "NUM2BIN where len(a) > 4"],
+["0x05 0xabcdef4243 6", "NUM2BIN 0x06 0xabcdef424300 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "pads output properly"],
+["0x05 0xabcdef4243 4", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "IMPOSSIBLE_ENCODING", "output too small"],
+["0x10 0x0102030405060708090A0B0C0D0E0F10 DUP CAT DUP CAT DUP CAT DUP CAT DUP CAT 0x08 0x0102030405060708 CAT 520", "NUM2BIN 0x10 0x0102030405060708090A0B0C0D0E0F10 DUP CAT DUP CAT DUP CAT DUP CAT DUP CAT 0x08 0x0102030405060708 CAT EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "520 byte 1st operand"],
+["0x05 0x0000000000 5", "NUM2BIN 0x05 0x0000000000 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "1st operand not minimally encoded"],
+["0x05 0x0001000000 3", "NUM2BIN 0x03 0x000100 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "OK", "1st operand can shrink"],
+["1 0x05 0x0500000000", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "UNKNOWN_ERROR", "2nd operand not minimally encoded"],
+["0x04 0xabcdef42 0x05 0xabcdef4243", "NUM2BIN", "P2SH,STRICTENC,MONOLITH_OPCODES", "UNKNOWN_ERROR", "2nd operand > 4 bytes"],
 
 ["BIN2NUM"],
 ["", "BIN2NUM 0 EQUAL", "P2SH,STRICTENC,MONOLITH_OPCODES", "INVALID_STACK_OPERATION", "BIN2NUM, empty stack"],
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -55,6 +55,7 @@
     {SCRIPT_ERR_PUBKEY_COUNT, "PUBKEY_COUNT"},
     {SCRIPT_ERR_INVALID_OPERAND_SIZE, "OPERAND_SIZE"},
     {SCRIPT_ERR_INVALID_NUMBER_RANGE, "INVALID_NUMBER_RANGE"},
+    {SCRIPT_ERR_IMPOSSIBLE_ENCODING, "IMPOSSIBLE_ENCODING"},
     {SCRIPT_ERR_INVALID_SPLIT_RANGE, "SPLIT_RANGE"},
     {SCRIPT_ERR_VERIFY, "VERIFY"},
     {SCRIPT_ERR_EQUALVERIFY, "EQUALVERIFY"},