diff --git a/src/FINUFFT.jl b/src/FINUFFT.jl
index dcce07b..f0ebfa2 100644
--- a/src/FINUFFT.jl
+++ b/src/FINUFFT.jl
@@ -51,6 +51,11 @@ function __init__()
         include("cufinufft_simple.jl")
         determine_cuda_status()
     end
+    # use the same lock as FFTW to ensure a thread-safe planning stage
+    @require FFTW="7a1cc6ca-52ef-59f5-83cd-3a7055c09341" begin
+        using .FFTW
+        FINUFFT.finufftlock = FFTW.fftwlock
+    end
 end
 
 end # module
diff --git a/src/errors.jl b/src/errors.jl
index 9222f55..981e7fd 100644
--- a/src/errors.jl
+++ b/src/errors.jl
@@ -22,6 +22,7 @@ const ERR_METHOD_NOTVALID        = 17
 const ERR_BINSIZE_NOTVALID       = 18
 const ERR_INSUFFICIENT_SHMEM     = 19
 const ERR_NUM_NU_PTS_INVALID     = 20
+const ERR_LOCK_FUNS_INVALID      = 21
 
 struct FINUFFTError <: Exception
     errno::Cint
@@ -79,6 +80,8 @@ function check_ret(ret)
         msg = "GPU shmem too small for subprob/blockgather parameters"
     elseif ret==ERR_NUM_NU_PTS_INVALID
         msg = "invalid number of nonuniform points: nj or nk negative, or too big (see defs.h)"
+    elseif ret==ERR_LOCK_FUNS_INVALID
+        msg = "fftw_(un)lock functions should be both null or both set"
     else
         msg = "error of type unknown to Julia interface! Check FINUFFT documentation"
     end
diff --git a/src/guru.jl b/src/guru.jl
index a0bbaa0..aeb5caf 100644
--- a/src/guru.jl
+++ b/src/guru.jl
@@ -1,5 +1,7 @@
 ### Guru Interfaces
 
+finufftlock = ReentrantLock()
+
 """
     p = finufft_default_opts()
     p = finufft_default_opts(dtype=Float32)
@@ -25,6 +27,13 @@ function finufft_default_opts(dtype::DataType=Float64)
                )
     end
 
+    lock_c = @cfunction(x -> lock(unsafe_pointer_to_objref(x)), Cvoid, (Ptr{Cvoid},))
+    unlock_c = @cfunction(x -> unlock(unsafe_pointer_to_objref(x)), Cvoid, (Ptr{Cvoid},))
+    
+    opts.fftw_lock_fun = lock_c
+    opts.fftw_unlock_fun = unlock_c
+    opts.fftw_lock_data = pointer_from_objref(finufftlock)
+
     return opts
 end
 
diff --git a/src/types.jl b/src/types.jl
index 46506fc..3cd06ec 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -96,6 +96,9 @@ mutable struct nufft_opts{T}
     maxbatchsize       :: Cint
     spread_nthr_atomic :: Cint
     spread_max_sp_size :: Cint
+    fftw_lock_fun      :: Ptr{Cvoid}
+    fftw_unlock_fun    :: Ptr{Cvoid}
+    fftw_lock_data     :: Ptr{Cvoid}
     nufft_opts{T}() where T <: finufftReal = new{T}()
 end
 # The above must match include/nufft_opts.h in FINUFFT.