diff --git a/sqlalchemy_firebird/base.py b/sqlalchemy_firebird/base.py
index c2467b3..2cbab1a 100644
--- a/sqlalchemy_firebird/base.py
+++ b/sqlalchemy_firebird/base.py
@@ -189,6 +189,18 @@ def get_column_specification(self, column, **kwargs):
 
         has_identity = column.identity is not None
 
+        type_compiler_instance = (
+            self.dialect.type_compiler_instance
+            if self.dialect.using_sqlalchemy2
+            else self.dialect.type_compiler
+        )
+
+        compiled_type = type_compiler_instance.process(
+            column.type,
+            type_expression=column,
+            identifier_preparer=self.preparer,
+        )
+
         if (
             column.primary_key
             and column is column.table._autoincrement_column
@@ -202,19 +214,9 @@ def get_column_specification(self, column, **kwargs):
             )
             and self.dialect.supports_identity_columns
         ):
-            colspec += " INTEGER GENERATED BY DEFAULT AS IDENTITY"
+            colspec += " %s GENERATED BY DEFAULT AS IDENTITY" % compiled_type
         else:
-            type_compiler_instance = (
-                self.dialect.type_compiler_instance
-                if self.dialect.using_sqlalchemy2
-                else self.dialect.type_compiler
-            )
-
-            colspec += " " + type_compiler_instance.process(
-                column.type,
-                type_expression=column,
-                identifier_preparer=self.preparer,
-            )
+            colspec += " " + compiled_type
             default_ = self.get_column_default_string(column)
             if default_ is not None:
                 colspec += " DEFAULT " + default_
diff --git a/test/test_compiler.py b/test/test_compiler.py
index 2d34b28..6c46f63 100644
--- a/test/test_compiler.py
+++ b/test/test_compiler.py
@@ -7,8 +7,10 @@
 from sqlalchemy import func
 from sqlalchemy import insert
 from sqlalchemy import Index
+from sqlalchemy import BigInteger
 from sqlalchemy import Integer
 from sqlalchemy import MetaData
+from sqlalchemy import SmallInteger
 from sqlalchemy import schema
 from sqlalchemy import select
 from sqlalchemy import String
@@ -442,6 +444,29 @@ def test_column_identity(self, pk):
             % (", PRIMARY KEY (y)" if pk else ""),
         )
 
+    @testing.combinations(
+        (Integer, "INTEGER"),
+        (BigInteger, "BIGINT"),
+        (SmallInteger, "SMALLINT"),
+        argnames="type_,expected_sql_type",
+    )
+    def test_autoincrement_primary_key_uses_column_type(
+        self, type_, expected_sql_type
+    ):
+        # Regression test for issue #88: the autoincrement primary key
+        # must use the column's declared type instead of hardcoded INTEGER.
+        m = MetaData()
+        t = Table(
+            "t",
+            m,
+            Column("id", type_, primary_key=True, autoincrement=True),
+        )
+        self.assert_compile(
+            schema.CreateTable(t),
+            "CREATE TABLE t (id %s GENERATED BY DEFAULT AS IDENTITY, "
+            "PRIMARY KEY (id))" % expected_sql_type,
+        )
+
     def test_column_identity_null(self):
         # all other tests are in test_identity_column.py
         m = MetaData()