diff --git a/CHANGELOG.md b/CHANGELOG.md
index 349a857..850baac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 2.2.5
+
+ - BugFix: Fix missed import in core.simple_instruction
+
 ## 2.2.4
 
  - BugFix: Found and added some missing floating point registers (`ft8` to `ft11`)
diff --git a/riscemu/core/exceptions.py b/riscemu/core/exceptions.py
index ad15072..9b7117e 100644
--- a/riscemu/core/exceptions.py
+++ b/riscemu/core/exceptions.py
@@ -187,7 +187,7 @@ def INS_NOT_IMPLEMENTED(ins):
 
 class NumberFormatException(RiscemuBaseException):
     def __init__(self, msg):
-        super().__init__()
+        super().__init__(msg)
         self.msg = msg
 
     def message(self):
diff --git a/riscemu/core/simple_instruction.py b/riscemu/core/simple_instruction.py
index efbf9e1..8172b8b 100644
--- a/riscemu/core/simple_instruction.py
+++ b/riscemu/core/simple_instruction.py
@@ -2,7 +2,13 @@
 from typing import Union, Tuple
 from functools import lru_cache
 
-from . import Instruction, T_RelativeAddress, InstructionContext, Immediate
+from . import (
+    Instruction,
+    T_RelativeAddress,
+    InstructionContext,
+    Immediate,
+    NumberFormatException,
+)
 from ..helpers import parse_numeric_argument
 
 _NUM_LABEL_RE = re.compile(r"[0-9][fb]")
@@ -32,7 +38,7 @@ def get_imm(self, num: int) -> Immediate:
 
         if _INT_IMM_RE.fullmatch(token):
             value = parse_numeric_argument(token)
-            return Immediate(abs_value=value, pcrel_value=value + self.addr)
+            return Immediate(abs_value=value, pcrel_value=value - self.addr)
 
         # resolve label correctly
         if _NUM_LABEL_RE.fullmatch(token):
@@ -43,7 +49,7 @@ def get_imm(self, num: int) -> Immediate:
         # TODO: make it raise a nice error instead
         if value is None:
             raise NumberFormatException(
-                "{} is neither a number now a known symbol!".format(token)
+                "{} is neither a number now a known symbol".format(token)
             )
         return Immediate(abs_value=value, pcrel_value=value - self.addr)
 
diff --git a/test/test_instruction.py b/test/test_instruction.py
new file mode 100644
index 0000000..6b0179a
--- /dev/null
+++ b/test/test_instruction.py
@@ -0,0 +1,53 @@
+from riscemu.core import InstructionContext, SimpleInstruction, NumberFormatException
+import pytest
+
+
+def test_int_and_hex_immediates():
+    ctx = InstructionContext()
+
+    ins = SimpleInstruction("addi", ("a0", "a1", "100"), ctx, 0x100)
+    ins_hex = SimpleInstruction("addi", ("a0", "a1", "0x10"), ctx, 0x100)
+
+    assert ins.get_reg(0) == "a0"
+    assert ins.get_reg(1) == "a1"
+    assert ins.get_imm(2).abs_value == 100
+    assert ins.get_imm(2).pcrel_value == 100 - 0x100
+
+    assert ins_hex.get_imm(2).abs_value == 0x10
+    assert ins_hex.get_imm(2).pcrel_value == 0x10 - 0x100
+
+
+def test_label_immediates():
+    ctx = InstructionContext()
+    ctx.labels["test"] = 100
+
+    ins = SimpleInstruction("addi", ("a0", "a1", "test"), ctx, 0x100)
+
+    assert ins.get_reg(0) == "a0"
+    assert ins.get_reg(1) == "a1"
+    assert ins.get_imm(2).abs_value == 100
+    assert ins.get_imm(2).pcrel_value == 100 - 0x100
+
+
+def test_numerical_labels():
+    ctx = InstructionContext()
+    ctx.numbered_labels["1"] = [0x100 - 4, 0x100 + 16]
+
+    ins = SimpleInstruction("addi", ("a0", "a1", "1b"), ctx, 0x100)
+
+    assert ins.get_reg(0) == "a0"
+    assert ins.get_reg(1) == "a1"
+    assert ins.get_imm(2).abs_value == 0x100 - 4
+    assert ins.get_imm(2).pcrel_value == -4
+
+
+def test_invalid_immediate_val():
+    ctx = InstructionContext()
+    ctx.labels["test"] = 100
+
+    ins = SimpleInstruction("addi", ("a0", "a1", "test2"), ctx, 0x100)
+
+    with pytest.raises(
+        NumberFormatException, match="test2 is neither a number now a known symbol"
+    ):
+        ins.get_imm(2)