diff --git a/llpython/byte_flow.py b/llpython/byte_flow.py
index 2201791..c86c6d1 100644
--- a/llpython/byte_flow.py
+++ b/llpython/byte_flow.py
@@ -118,7 +118,7 @@ class BytecodeFlowBuilder (BasicBlockVisitor):
         assert arg is None
         return self._op(i, op, loop_i + loop_arg + 3)
 
-    #op_BUILD_CLASS = _op
+    op_BUILD_CLASS = _op
     op_BUILD_LIST = _op
     op_BUILD_MAP = _op
     op_BUILD_SLICE = _op
@@ -147,7 +147,15 @@ class BytecodeFlowBuilder (BasicBlockVisitor):
     #op_EXTENDED_ARG = _op
     op_FOR_ITER = _op
     op_GET_ITER = _op
-    op_IMPORT_FROM = _op
+
+    def op_IMPORT_FROM (self, i, op, arg):
+        # References top of stack without popping, so we can't use the
+        # generic machinery.
+        opname = self.opmap[op][0]
+        ret_val = i, op, opname, arg, [self.stack[-1]]
+        self.stack.append(ret_val)
+        return ret_val
+
     op_IMPORT_NAME = _op
     op_IMPORT_STAR = _op
     op_INPLACE_ADD = _op
diff --git a/llpython/opcode_util.py b/llpython/opcode_util.py
index efd0c5c..1de6507 100644
--- a/llpython/opcode_util.py
+++ b/llpython/opcode_util.py
@@ -31,9 +31,9 @@ OPCODE_MAP = {
     'BINARY_TRUE_DIVIDE': (2, 1, None),
     'BINARY_XOR': (2, 1, None),
     'BREAK_LOOP': (0, None, 1),
-    'BUILD_CLASS': (None, None, None),
+    'BUILD_CLASS': (3, 1, None),
     'BUILD_LIST': (-1, 1, None),
-    'BUILD_MAP': (None, None, None),
+    'BUILD_MAP': (-1, 1, None),
     'BUILD_SET': (None, None, None),
     'BUILD_SLICE': (None, None, None),
     'BUILD_TUPLE': (-1, 1, None),
@@ -62,7 +62,7 @@ OPCODE_MAP = {
     'FOR_ITER': (1, 1, 1),
     'GET_ITER': (1, 1, None),
     'IMPORT_FROM': (None, None, None),
-    'IMPORT_NAME': (None, None, None),
+    'IMPORT_NAME': (2, 1, None),
     'IMPORT_STAR': (1, None, 1),
     'INPLACE_ADD': (2, 1, None),
     'INPLACE_AND': (2, 1, None),