diff --git a/.travis.yml b/.travis.yml
index 17ae020..ad4166c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,10 +8,7 @@ addons:
 python:
 - '3.6'
 install:
-- pip install -r requirements.txt
-- pip install python-coveralls
-- pip install pytest-cov
-- pip install -e .
+- pip install -e .[TEST]
 script: py.test --cov=hwtypes tests/
 after_success: coveralls
 deploy: &pypi
@@ -21,4 +18,4 @@ deploy: &pypi
     secure: 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
   on:
     branch: master
-    tags: true
+    tags: true
\ No newline at end of file
diff --git a/hwtypes/__init__.py b/hwtypes/__init__.py
index 6858443..fcd12a3 100644
--- a/hwtypes/__init__.py
+++ b/hwtypes/__init__.py
@@ -1,9 +1,25 @@
-from .bit_vector import *
-from .bit_vector_abc import *
 from .adt import *
-from .smt_bit_vector import *
-from .z3_bit_vector import *
+from .bit_vector_abc import *
+from .bit_vector import *
 from .fp_vector_abc import *
-from .fp_vector import *
-from .smt_fp_vector import *
 from .modifiers import *
+
+try:
+    from .fp_vector import *
+except ImportError:
+    pass
+
+try:
+    from .smt_bit_vector import *
+except ImportError:
+    pass
+
+try:
+    from .z3_bit_vector import *
+except ImportError:
+    pass
+
+try:
+    from .smt_fp_vector import *
+except ImportError:
+    pass
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 4cb8cfb..0000000
--- a/requirements.txt
+++ /dev/null
@@ -1 +0,0 @@
-pysmt
diff --git a/setup.py b/setup.py
index 33ab945..cb57e32 100644
--- a/setup.py
+++ b/setup.py
@@ -14,6 +14,12 @@
 with open("README.md", "r") as fh:
     long_description = fh.read()
 
+FP_requries   = ['gmpy2']
+SMT_requires  = ['pysmt']
+Z3_requries   = ['z3-solver']
+ALL_requires  = FP_requries+SMT_requires+Z3_requries
+TEST_requires = ALL_requires+['pytest-cov']
+
 setup(
     name='hwtypes',
     url='https://github.com/leonardt/hwtypes',
@@ -26,8 +32,15 @@
     packages=[
         "hwtypes",
     ],
-    install_requires=['pysmt', 'z3-solver', 'gmpy2'],
+    install_requires=[],
+    extras_require={
+        'FP'  : FP_requries,
+        'SMT' : SMT_requires,
+        'Z3'  : Z3_requries,
+        'ALL' : ALL_requires,
+        'TEST': TEST_requires,
+    },
     long_description=long_description,
-    long_description_content_type="text/markdown"
-    # python_requires='>=3.6'
+    long_description_content_type="text/markdown",
+    python_requires='>=3.6',
 )