diff --git a/Dockerfile b/Dockerfile
index c842dbb..c25371b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -30,8 +30,8 @@ RUN curl -o Miniconda3-latest-Linux-x86_64.sh https://repo.continuum.io/minicond
   && ./Miniconda3-latest-Linux-x86_64.sh -b -p "${MINICONDA_HOME}" \
 && rm Miniconda3-latest-Linux-x86_64.sh
 COPY conda.txt conda.txt
-RUN conda install -y --file=conda.txt
-RUN conda clean -y -i -l -p -t && \
+RUN conda install -y --file=conda.txt && \
+    conda clean -y -i -l -p -t && \
     rm -f conda.txt
 COPY pip.txt pip.txt
 RUN pip install -r pip.txt && \
diff --git a/conda.txt b/conda.txt
index 24ce15a..22773da 100644
--- a/conda.txt
+++ b/conda.txt
@@ -1 +1 @@
-numpy
+numpy==1.15.3
diff --git a/neuralstyle/algorithms.py b/neuralstyle/algorithms.py
index 79976e3..1dfba59 100644
--- a/neuralstyle/algorithms.py
+++ b/neuralstyle/algorithms.py
@@ -351,7 +351,11 @@ def targetshape(content, size=None):
 
 def gpuname():
     """Returns the model name of the first available GPU"""
-    gpus = GPUtil.getGPUs()
+    try:
+        gpus = GPUtil.getGPUs()
+    except:
+        LOGGER.warning("Unable to detect GPU model. Is your GPU configured? Are you running with nvidia-docker?")
+        return "UNKNOWN"
     if len(gpus) == 0:
         raise ValueError("No GPUs detected in the system")
     return gpus[0].name
@@ -365,6 +369,6 @@ def maxtile(alg="gatys"):
     """
     gname = gpuname()
     if gname not in GPUCONFIG:
-        LOGGER.warning("Unknown GPU model %s, will use default tiling parameters")
+        LOGGER.warning(f"Unknown GPU model {gname}, will use default tiling parameters")
         gname = "default"
     return GPUCONFIG[gname][alg]
diff --git a/pip.txt b/pip.txt
index 7ee527d..53b3f19 100644
--- a/pip.txt
+++ b/pip.txt
@@ -1 +1 @@
-gputil
+gputil==1.3.0